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The spleen is the largest ductless gland and largest single lymphatic organ in the human body. The main functions of the spleen are immunologic surveillance and red blood cell breakdown. The spleen can be affected by diseases of different origins, such as inflammatory, congenital, infectious, neoplastic, and vascular diseases. Ultrasonography (US) is usually used as the 1st-line imaging modality due to its easy accessibility and lack of ionizing radiation, but CT and MRI with contrast can also be helpful. Contrasted imaging modalities can delineate lesions and help differentiate disorders.
The mediastinum is the central part of the chest cavity containing many vital structures, such as the heart, great vessels, trachea, thoracic esophagus, lymph nodes, multiple nerves, sympathetic chains, and thoracic spine. Mediastinal pathology (e.g., masses) can be noted on conventional radiographs as part of evaluating chest-related symptoms, or it can be incidentally detected. To elucidate the characteristics of the mediastinal abnormality, further imaging studies are warranted. Common additional modalities are CT and MRI.
Diagnostic modalities such as chest X-rays provide static images of the thoracic cavity, including the lungs and airways. While providing a wealth of anatomical information necessary for the diagnosis of pulmonary disease, chest X-rays do not give much information about the individual's respiratory function. Pulmonary function tests are a group of diagnostic procedures yielding useful, quantifiable information about the rate of the flow of air through the individual's airways, lung capacity, and the efficiency of gas exchange in relation to time. The most commonly utilized tests include spirometry (before and after bronchodilator use), lung volumes, and quantitation of diffusing capacity for carbon monoxide (CO). The tests can be influenced by the individual's effort/fatigue, disease state, or anatomical malformation.
In the pediatric population, imaging often plays a critical diagnostic role, especially in diagnosing congenital anomalies. In children, CT scans are avoided if at all possible due to the high risk of radiation exposure. In addition, both CT and (especially) MRI require children to hold still for significant periods of time and often require sedation to complete the study. For these reasons, plain radiography (often with contrast), fluoroscopy, and ultrasound are the imaging modalities of choice for most suspected cases involving GI pathology. Some conditions that can be diagnosed using imaging include hypertrophic pyloric stenosis, necrotizing enterocolitis, midgut malrotation with or without volvulus, intestinal atresia intussusception, appendicitis, Hirschsprung disease, mesenteric lymphadenitis, and obstructions of the biliary tree.
Chest abnormalities are a common presenting pathology of the pediatric population. Imaging modalities such as chest X-rays are the initial diagnostic test of choice used in urgent/emergent pediatric cases. Imaging modalities aid in differentiating the causes of respiratory distress in infants and finding the underlying infectious, traumatic, or congenital disorder. Computed tomography (CT) is a useful adjunctive modality in the pediatric population when conventional radiography fails to adequately characterize pathology. Given the common occurrence with many cardiac or vascular anomalies, specific protocols are necessary to highlight potentially abnormal anatomical structures. Pediatric chest imaging is a multimodality process at most centers used to help answer clinical questions and adequately care for individuals.
Imaging of the intestines is typically performed utilizing a multimodal approach, with clinical suspicion being the primary indicator for which study should be completed and in what order. There are also many differences between outpatient imaging versus emergency or inpatient imaging of the intestines. Imaging varies widely based on the patient's history, symptoms, and physical exam findings. The patient's age will also play a factor in the modality chosen. For example, appendicitis is typically 1st evaluated via ultrasound in the pediatric population versus CT in adults.
The hepatobiliary system is composed of the liver, gallbladder, and bile ducts (within the liver and external to the liver). The liver produces bile, which is a fluid made of cholesterol, phospholipids, conjugated bilirubin, bile salts, electrolytes, and water. Bile, which assists in digestion and helps eliminate waste products, is stored in the gallbladder. The hepatobiliary system can be affected by infections, cysts, solid masses, ischemia, and mechanical flow obstruction, which mandate the presence of reliable imaging tests to determine the etiology. The methods that evaluate structural changes in the liver and biliary tract include ultrasonography, CT scan, and MRI (including magnetic resonance cholangiopancreatography). Additionally, cholescintigraphy, a functional imaging study, helps identify gallbladder pathology by tracking the biliary pathway.
Imaging of the internal female reproductive organs (including the uterus, ovaries, and fallopian tubes) is indicated to diagnose common gynecologic complaints, most commonly in cases of abnormal bleeding, pelvic pain, and to evaluate masses, congenital anomalies, and infertility. Ultrasound is almost always the 1st-line imaging modality of choice, whereas MRI is typically reserved for complicated or indeterminate cases as a follow-up. Computed tomography is almost never used for primary gynecologic assessments. Fallopian tubes are not visible on either ultrasound or MRI if they are normal. The best way to assess tubal patency is by using hysterosalpingography, a fluoroscopic exam in which a dye is injected into the uterine cavity, followed by the study of its flow through the fallopian tubes.
The renal system is composed of 2 kidneys, 2 ureters, a bladder, and a urethra. These structures function to filter blood and excrete urine, which contains waste products of metabolism. Varying conditions such as infections, cysts, solid masses, ischemia, and mechanical obstruction can affect the renal system. Evaluation of diseases rely on imaging methods such as radiography, ultrasonography, CT, and MRI. Some of these are also used to guide tissue sampling (e.g., renal biopsy).
Female breasts, made of glandular, adipose, and connective tissue, are hormone-sensitive organs that undergo changes along with the menstrual cycle and during pregnancy. Breasts may be affected by various diseases, in which different imaging methods are important to arrive at the correct diagnosis and management. Mammography is used for breast cancer screening and diagnostic evaluation of various breast-related symptoms. Ultrasonography is rarely used for screening, but it is typically used for diagnostic workup and during procedures (e.g., breast biopsy). MRI of the breasts is used as a supplementary screening tool for those at high risk for developing breast cancer. Additionally, in individuals with breast implants, inconclusive mammographic and/or breast ultrasound findings, and diagnosed breast cancer needing evaluation pretreatment and posttreatment, MRI is an important breast radiologic tool.
Congestive heart failure (CHF) is a progressive syndrome characterized by the failure of the heart to maintain the metabolic demands of the body either due to systolic or diastolic dysfunction. Treatment of CHF is centered around lifestyle modifications (salt and fluid restriction, smoking cessation, and weight loss) and pharmacologic management. Acute worsening of heart failure is often secondary to other medical conditions and is managed with aggressive diuresis and interventions to support cardiac and ventilatory functions. Angina is defined as chest pain or discomfort resulting from myocardial ischemia. Therapy for angina is targeted at limiting platelet aggregation and adhesion (with antiplatelet agents), reducing O2 demand (with beta-blockers), reducing preload (with nitrates), and preventing the progression of atherosclerotic disease (using statin therapy), along with the management of comorbidities.
Non-Hodgkin lymphomas (NHLs) are a diverse group of hematologic malignancies that are clonal proliferative disorders of mature or progenitor B cells, T cells, or natural killer (NK) cells. Most pediatric cases are aggressive and high-grade (but curable); in adults, low-grade subtypes are more common. Like Hodgkin lymphoma, which has distinct pathologic features and treatments, NHL often presents with constitutional signs of fever, night sweats, and weight loss. Clinical features include lymphadenopathy and hepatosplenomegaly, but some individuals present with extranodal involvement and abnormal lab findings. B-cell NHLs include diffuse large B-cell lymphoma, follicular lymphoma, Burkitt lymphoma, mantle cell lymphoma, and marginal zone lymphoma. T-cell NHLs include adult T-cell lymphoma and mycosis fungoides. Diagnosis is made by lymph node biopsy, bone marrow biopsy, or both. Management is with chemotherapy or targeted drugs. Radiation therapy is used in adults but not in children, and stem cell transplantation is used for patients with aggressive disease.
Diagnostic procedures in gynecology are useful in identifying the presence of disease, determining the progression of disease, and monitoring the response of the organs to treatment. The major diagnostic procedures include speculum examinations, sonography (ultrasound), colposcopy, cervical biopsy and endocervical curettage, loop electrosurgical excision procedures, vulvar biopsy, endometrial biopsy, hysteroscopy, and hysterosalpingography (HSG). All of these procedures can be performed in the office setting or in a radiology suite, though in certain situations they are performed in the OR if more sedation or increased monitoring is required.
The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The fallopian tubes receive an ovum after ovulation and help move it and/or a fertilized embryo toward the uterus via ciliated cells lining the tubes and peristaltic movements of its smooth muscle. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Externally, the cervix is lined by stratified squamous cells; however, the cervical canal is lined by columnar epithelium. The transition point is known as the squamocolumnar junction, which is the site of most cervical cancers. These organs are supplied by the uterine and ovarian arteries and innervated by the autonomic nervous system.
Spinal cord injuries are complex injuries that involve damage to the neural tissue within the spinal canal. Spinal cord injuries are commonly the result of trauma. Clinical presentation varies depending on the site of injury and on whether the injury is complete or incomplete. Diagnosis is by clinical exam and imaging. Management is 2-fold, with immediate supportive care and stabilization of spine followed by long-term rehabilitation with physiotherapy and treatment of complications. Spinal cord injuries are associated with multisystem complications.
The adult human body is made up of 60% water and is divided into extracellular and intracellular fluid compartments. Extracellular fluid is present outside the cells and makes up â…“ of the total body water. Intracellular fluid is present inside the cells and makes up â…” of the total body water. Intracellular and extracellular fluids are separated into compartments by semipermeable membranes, and the transport of fluid and ions is maintained by channels in the cell membrane. Each compartment contains different concentrations of ions and osmolar molecules. The relative charge and osmolarity are maintained rigorously by the transport of water and substances between compartments. Hypernatremia, hyponatremia, and edema are the clinical conditions arising from disturbances in the maintenance of osmolarity of the body fluid compartments.
Vascular surgery is the specialized field of medicine that focuses on the surgical management of the pathologies of the peripheral circulation. The main goal of most vascular procedures is to restore circulatory function to the affected vessels by relieving occlusions or by redirecting blood flow (e.g., bypass). Surgical intervention is either open or endovascular. Vascular interventions require a multidisciplinary approach, including vascular surgeons, interventional radiologists, anesthesiologists (or anesthetists), nurses, physiotherapists, and occupational therapists.
Acute disseminated encephalomyelitis (ADEM) is an immune-mediated, inflammatory, monophasic, demyelinating condition that affects the white matter of the brain and spinal cord. As a rapidly progressive post-infectious encephalomyelitis, ADEM is characterized by demyelination in the brain and spinal cord as a result of inflammation following infection or immunization.
Spinal disk herniation (also known as herniated nucleus pulposus) describes the expulsion of the nucleus pulposus through a perforation in the annulus fibrosus of the intervertebral disk. Spinal disk herniation is an important pain syndrome with the potential for neurologic impairment and is most commonly caused by degenerative disk disease. Clinical presentation depends on the presence or absence of spinal cord or nerve root compression and the downstream neurologic sequelae (e.g., radicular pain, muscle weakness, sensory deficit, reflex deficit). Diagnosis is initially clinical and can be confirmed with diagnostic imaging (e.g., MRI). Management can range from conservative to surgical, depending on the situation.
A tachyarrhythmia is a rapid heart rhythm, regular or irregular, with a rate > 100 beats/min. Tachyarrhythmia may or may not be accompanied by symptoms of hemodynamic change. Pathologic tachyarrhythmias resulting in hemodynamic instability can be caused by intrinsic cardiac abnormalities, systemic diseases, or medication toxicity. Supraventricular arrhythmias are called narrow-complex tachycardias and originate in the sinoatrial (SA) node, atrial myocardium, or atrioventricular (AV) node. Ventricular arrhythmias originate below the AV node and are characterized by a wide QRS complex. Diagnosis is made by physical exam and ECG. Management is directed toward the type of tachyarrhythmia present and its underlying cause.
The branchial arches, also known as pharyngeal or visceral arches, are embryonic structures seen in the development of vertebrates that serve as precursors for many structures of the face, neck, and head. These arches are composed of a central core of mesoderm, which is covered externally by ectoderm and internally by endoderm. Indentations between arches are known as the pharyngeal clefts, or grooves, externally and the pharyngeal pouches internally. Each pharyngeal arch contains cartilage and muscular components, which are supplied by a cranial nerve (derived from neural crest cells), and an artery, known as a pharyngeal aortic arch. Some of these aortic arches go on to form the great vessels near the heart.
Both gastrulation and neurulation are critical events that occur during the 3rd week of embryonic development. Gastrulation is the process by which the bilaminar disc differentiates into a trilaminar disc, made up of the 3 primary germ layers: the ectoderm, mesoderm, and endoderm. During this process, a structure called the notochord is formed in the midline in the mesodermal layer; the notochord is critical in inducing neurulation. Neurulation is the process by which some of the ectoderm in the trilaminar embryo develops into the neural tube and neural crest cells, which will go on to form all of the neural tissue in the body. This process is completed by the end of the 3rd week.
The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 â€œhipâ€ bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. The pelvic ring joints include the pubic symphysis anteriorly and the sacroiliac joints posteriorly. The hip bones are made up of 3 fused bones: the pubis, ischium, and ilium. The pelvic cavity houses various GI, urinary, and reproductive structures, which are supported by the muscles and connective tissue of the pelvic floor. The female pelvis, making accommodations for childbirth, is generally wider and larger than the male pelvis.
Liver function tests, also known as hepatic function panels, are one of the most commonly performed screening blood tests. Such tests are also used to detect, evaluate, and monitor acute and chronic liver diseases. Liver function tests assess the levels of various hepatic proteins and enzymes to determine the state of liver metabolic activity, homeostasis, bile metabolism, and protein synthesis capacity. The standard hepatic panel includes the levels of total protein, bilirubin, albumin, ALT, AST, AST/ALT ratio, and alkaline phosphatase (ALP).
The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. The bladder acts as a reservoir for urine until micturition is appropriate. Regulation of micturition relies on the CNS and the spinal cord.
Sickle cell disease (SCD) is a group of genetic disorders in which an abnormal Hb molecule (HbS) transforms RBCs into sickle-shaped cells, resulting in chronic anemia, vasoocclusive episodes, pain, and organ damage. Sickle cell trait, which is the heterozygous condition, is the only 1 of the group that is generally benign and rarely associated with serious SCD-like complications. Triggers such as stress and hypoxia can induce or worsen the sickling of RBCs. Individuals with SCD are susceptible to infection, infarction of various organs, and bone marrow aplasia; lung involvement in acute chest syndrome can be rapidly fatal. Sickle cells can usually be seen on the peripheral blood smear, but Hb electrophoresis is needed for diagnosis. The management of painful episodes consists of IV fluids and analgesics, and in severe episodes, exchange transfusions may be required. Survival is improved by vaccination against bacterial infections, prophylactic antibiotics, and aggressive treatment of infections.
Ovaries are the paired gonads of the female reproductive system that contain haploid gametes known as oocytes. The ovaries are located intraperitoneally in the pelvis, just posterior to the broad ligament, and are connected to the pelvic sidewall laterally by the suspensory ligament of the ovary and to the uterus medially by the utero-ovarian ligament. These organs function to secrete hormones (estrogen and progesterone) and to produce the female germ cells (oocytes), which are expelled and then â€œcapturedâ€ by the uterine tubes. The primary blood supply to the ovary is provided by the ovarian artery, a direct branch of the abdominal aorta; the ovarian artery anastomoses with the ascending branch of the uterine artery, providing excellent collateral blood flow.
The cerebellum, Latin for "little brain", is located in the posterior cranial fossa, dorsal to the pons and midbrain, and its principal role is in the coordination of movements. The cerebellum consists of 3 lobes on either side of its 2 hemispheres and is connected in the middle by the vermis. Three paired peduncles link the cerebellum to the brainstem and diencephalon. Much like the cerebral cortex, the cerebellum has a cortex of gray matter on the surface.
The heart is a 4-chambered muscular pump made primarily of cardiac muscle tissue. The heart is divided into 4 chambers: 2 upper chambers for receiving blood from the great vessels, known as the right and left atria, and 2 stronger lower chambers, known as the right and left ventricles, which pump blood throughout the body. Blood flows through the heart in 1 direction, moving from the right side of the heart, through the lungs, and then returning to the left side of the heart, where it is pumped out to the rest of the body. As blood moves through the heart, 4 important valves prevent backflow. The heart muscle itself is supplied by the coronary arteries. The heart also has its own conduction system, triggering its own rhythmic contractions.
Juvenile idiopathic arthritis (JIA), formerly known as juvenile rheumatoid arthritis, is a heterogeneous group of inflammatory diseases characterized by inflammation of 1 or more joints and is the most common pediatric rheumatic disease. Juvenile idiopathic arthritis is classified according to its clinical presentation, and diagnosis is made with examination findings as well as confirmatory lab testing showing evidence of inflammation and characteristic X-ray findings. Treatment is directed at preventing loss of function and controlling or limiting joint damage, with a variable prognosis depending on the type.
Nephritic syndrome is a broad category of glomerular diseases characterized by glomerular hematuria, variable loss of renal function, and hypertension. These features are in contrast to those of nephrotic syndrome, which includes glomerular diseases characterized by severe proteinuria, although there is sometimes overlap of > 1 glomerular disease in the same individual. The clinical presentations of nephritic syndrome are highly varied, from asymptomatic with urinary abnormalities to life-threatening critical illness. Diagnosis is suggested by hematuria, mild-to-moderate proteinuria, and certain serologies (e.g., ANCA); kidney biopsy is necessary in most cases. Management varies as widely as the clinical presentations, from watchful waiting in mild cases to immunosuppression and plasmapheresis in aggressive disease.
The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. The spinal cord is divided into cervical, thoracic, lumbar, and sacral regions, though because the spinal cord is shorter than the vertebral column, these regions do not line up with their corresponding vertebral levels. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Like the brain, the spinal cord is surrounded by 3 layers of connective tissue, collectively known as the meninges; these layers are the dura mater, arachnoid mater, and pia mater. The spinal cord is supplied by 1 anterior and 2 posterior spinal arteries.
Nephrotic syndrome is characterized by severe proteinuria, hypoalbuminemia, and peripheral edema. In contrast, the nephritic syndromes present with hematuria, variable loss of renal function, and hypertension, although there is sometimes overlap of > 1 glomerular disease in the same individual. The primary etiologies of nephrotic syndrome are minimal change disease, membranous nephropathy, and focal segmental glomerulosclerosis. The clinical presentation of nephrotic syndrome includes proteinuria (> 3.5 g/day), hypoalbuminemia (< 3 g/dL), and peripheral edema. Other frequently observed clinical findings are hyperlipidemia and thrombotic disease. Diagnosis is suggested by the clinical findings, and kidney biopsy is necessary in most cases. Management varies with the etiology and usually involves glucocorticoids or other immunosuppressant drugs.
Polyneuropathy is any disease process affecting the function of or causing damage to multiple nerves of the peripheral nervous system. There are numerous etiologies of polyneuropathy, most of which are systemic and the most common of which is diabetic neuropathy. The clinical presentation varies by etiology as well as classification of the polyneuropathy, but generally manifests as sensorimotor disturbances (pain, paresthesia, numbness, weakness, and loss of coordination and balance), which have a gradual onset and progressive course. Distal nerves are affected most commonly, but the disease process may progress proximally with time or progression of the underlying etiologic disease entity. Diagnosis is made clinically, but laboratory studies, electrodiagnostic testing, and/or nerve biopsy may be required in some cases. Management varies depending on the etiology.
Fever is defined as a higher-than-normal body temperature. In modern medicine, fever is defined as a temperature > 38Â°C (100.4Â°F). It is a common symptom in the pediatric population as an isolated symptom or accompanied by other findings that can help narrow the differential diagnosis. Fever is most commonly the bodyâ€™s response to infectious processes; however, it can also be seen in other pathologic processes. In neonates and very young infants, the clinical presentation lacks specificity, so more diagnostic aids are deployed to rule out severe bacterial infection (SBI) and to begin treatment according to age and clinical evolution.
Neurosurgery is a specialized field focused on the surgical management of pathologies of the brain, spine, spinal cord, and peripheral nerves. General neurosurgery includes cases of trauma and emergencies. There are a number of specialized neurosurgical practices, including oncologic neurosurgery, spinal neurosurgery, and pediatric neurosurgery. Common neurosurgery cases treat tumors, masses, herniations, various types of hemorrhages, and radicular pain. Although neurosurgery is a surgical specialty, neurosurgeons must be very competent in neurology, critical care, trauma care, and radiology.
Neuropathy is a nerve pathology presenting with sensory, motor, or autonomic impairment secondary to dysfunction of the affected nerve. The peripheral nerves (outside the brain and spinal cord), are derived from several plexuses, with the brachial and lumbosacral plexuses supplying the major innervation to the extremities. Mononeuropathy (affecting a single nerve) and plexopathy (affecting the plexus) can occur from trauma, compression, and systemic diseases. The clinical presentation varies according to location, type of nerves affected, and cause of the damage. Diagnosis requires a thorough physical examination, and diagnostic tests include laboratory tests, imaging and a confirmatory nerve conduction study, and electromyography. Management depends on the etiology but centers around physical therapy, supportive care, and treatment of underlying issues.
Brain aneurysms, also known as intracranial or cerebral aneurysms, are dilations of the arteries along points of weakness in the brain. The majority of the aneurysms are berry (saccular) in nature and located within the anterior circulation of the circle of Willis. Unruptured aneurysms are typically asymptomatic, unless the aneurysm compresses surrounding structures. The majority of these aneurysms are detected on rupture and presentation of a subarachnoid hemorrhage (SAH). Rarely, they may be detected incidentally on brain imaging done for other reasons. Diagnosing an aneurysm is done via imaging with CTA or MRA. Management depends on the size, risk of rupture, risk of intervention complications, and individual preference. This may include risk factor modifications, surveillance with serial imaging, and interventional measures (such as surgical clipping or endovascular coiling). Ruptured aneurysms carry a high morbidity and mortality rate.
Staphylococcus is a medically important genera of Gram-positive, aerobic cocci. These bacteria form clusters resembling grapes on culture plates. Staphylococci are ubiquitous for humans, and many strains compose the normal skin flora. Staphylococcus aureus is the most virulent species; S. epidermidis and S. saprophyticus are less virulent but are also clinically significant. Infection can cause a wide array of disease, including cellulitis, abscesses, endocarditis, osteomyelitis, and medical device infections. Toxins formed by S. aureus can cause gastroenteritis, SSSS, and toxic shock syndrome (TSS). Antibiotic management varies based on the type of infection, severity, and sensitivity data.
Immunosuppressants are a class of drugs widely used in the management of autoimmune conditions and organ transplant rejection. The general effect is dampening of the immune response. There are multiple targets in the immune system, as well as varied mechanisms in inhibiting inappropriate immune activity. Biologic agents are medications derived from living organisms that target particular components of the immune system. The targets can be tumor necrosis factor (TNF), interleukins (ILs), or B- or T-cell activity. Calcineurin inhibitors halt the activity of calcineurin, a phosphatase involved in T-cell activation. Corticosteroids interfere with the cell cycle of inflammatory cells and modify the activity of other immune components. mTOR inhibitors are proliferation signal inhibitors, reducing immune-cell proliferation. Some immunosuppressants, such as cytotoxic agents, have antineoplastic activity; these are used in rheumatoid arthritis, as prophylaxis for transplant rejection, and for malignant diseases.
Candida is a genus of dimorphic, opportunistic fungi. Candida albicans is part of the normal human flora and is the most common cause of candidiasis. Risk factors for infection include conditions or agents that may lead to an immunocompromised state, disruption of the normal flora, and/or disturbance of the mucosal barrier. The clinical presentation varies and can include localized mucocutaneous infections (e.g., oropharyngeal, esophageal, intertriginous, and vulvovaginal candidiasis) and invasive disease (e.g., candidemia, intraabdominal abscess, pericarditis, and meningitis). The diagnosis is made by identifying Candida on KOH preparation, cultures, or tissue biopsy. Treatment depends on the extent and site of infection, and includes topical or systemic antifungal medications
Before the developing blastocyst reaches the uterine wall, it needs to undergo several stages of differentiation. After a continuous process of cleavage and compaction, the morula gives rise to the trophoblast and embryoblast, which are the primary components of the blastocyst. Uterine fluid passes through the zona pellucida to form the blastocyst cavity. When the blastocyst reaches the endometrium, implantation begins by the trophoblast dividing into the cytotrophoblast and syncytiotrophoblast, with the syncytiotrophoblast primarily being responsible for invading the endometrium. The embryoblast divides into the epiblast and hypoblast, which are responsible for creating the amniotic cavity and yolk sac, respectively.
The kidneys are a pair of bean-shaped organs located retroperitoneally against the posterior wall of the abdomen on either side of the spine. As part of the urinary tract, the kidneys are responsible for blood filtration and excretion of water-soluble waste in the urine. The kidneys also play a major role in homeostatic processes, including electrolyte concentration, blood pressure, and acid–base regulation. Grossly, they consist of an outer cortex and inner medulla. Microscopic functional units known as nephrons filter the blood through a structure called the glomerulus, and this filtrate is then modified and concentrated as it moves through a complex tubular system. The renal arteries supply the kidneys via a central opening, known as the renal hilum, on its medial side; large renal veins empty directly into the vena cava.
Gout medications include antiinflammatory and urate-lowering medications. Colchicine is an antiinflammatory medication that can be used for acute gout flares. The urate-lowering drug classes include the xanthine oxidase inhibitors, uricosuric agents, and uricases. These medications are beneficial for the prevention of gout exacerbations and work through a variety of mechanisms. Xanthine oxidase inhibitors are the most commonly used urate-lowering therapy; these work by inhibiting the enzyme necessary for the conversion of purines to uric acid. Uricosuric agents reduce reabsorption of uric acid by the proximal tubule, thereby increasing renal excretion. Lastly, the urases are recombinant enzymes that metabolize uric acid to allantoin. In addition to gout, urate-lowering treatment can also be used for other indications, such as the prevention of tumor lysis syndrome and uric acid nephrolithiasis.
Brown-Séquard syndrome (BSS) is a rare neurologic injury that causes hemisection of the spinal cord, resulting in weakness and paralysis of one side of the body and sensory loss on the opposite side. This syndrome is most often due to trauma, but it may also occur with disc herniation, hematoma, or tumor. Clinical presentation is consistent with ipsilateral damage to the corticospinal tracts and posterior columns (weakness, loss of proprioception, and vibration sensation) below the level of the lesion, and contralateral anterior column symptoms owing to the unilateral involvement of the spinothalamic tract (loss of pain and temperature sensation). Diagnosis is confirmed with MRI. Management depends on the etiology and site of injury, and timely intervention is associated with a favorable prognosis and recovery.
Membranoproliferative glomerulonephritis (MPGN) is also known as mesangiocapillary glomerulonephritis. Membranoproliferative glomerulonephritis is a pattern of glomerular injury characterized by mesangial hypercellularity, endocapillary proliferation, and thickening of the glomerular basement membrane (double contour formation). The changes are due to the deposition of Igs, complement factors, or both, in the glomerular mesangium and along the glomerular capillary walls. The pathogenic variants include immune complex/monoclonal Ig-mediated (e.g., from infections, autoimmune diseases) and complement-mediated MPGN. In rare cases, MPGN is not associated with Igs and the complement system, such as in the case of endothelial injury. With multiple etiologies, the presentation and clinical course vary. Presenting features can be asymptomatic proteinuria and hematuria, nephrotic syndrome, nephritic syndrome, or chronic renal failure. Definitive diagnosis requires renal biopsy, although additional laboratory and imaging tests may point to the associated disease. Treatment is based on the underlying cause. Steroids, immunosuppressants, and kidney transplantation are among the commonly used treatment modalities.
Anticonvulsant drugs are pharmacological agents used for seizure control and/or to prevent seizure episodes. Anticonvulsants encompass various drugs with different mechanisms of action, including ion-channel (Na+, calcium) blocking and inhibition of GABA reuptake. Second-generation anticonvulsants exert their effects via these mechanisms and are associated with good efficacy, fewer toxic effects, and better tolerability, and generally do not require blood level monitoring. Medications in this class include felbamate, gabapentin, pregabalin, lamotrigine, levetiracetam, oxcarbazepine, tiagabine, topiramate, zonisamide, and lacosamide. Anticonvulsant drugs are indicated for focal seizures, generalized tonic-clonic seizures, myoclonic seizures, and Lennox-Gastaut syndrome. Some anticonvulsants are also indicated in conditions unrelated to seizures (e.g., bipolar disorder). The most common adverse effects include dizziness, headache, and somnolence.
The testicles, also known as the testes or the male gonads, are a pair of egg-shaped glands suspended within the scrotum. The testicles have multiple layers: an outer tunica vaginalis, an intermediate tunica albuginea, and an innermost tunica vasculosa. The testicles are composed of testicular lobules (contain interstitial tissue) and seminiferous tubules (produce spermatozoa). Blood supply to the testicles is primarily provided by the testicular artery. Venous drainage is through testicular veins.
The ear is a sensory organ responsible for the sense of hearing and balance. Anatomically, the ear can be divided into 3 parts: the outer ear, the middle ear, and the inner ear. The outer ear consists of the auricle and ear canal. The middle ear houses the tympanic structures and ossicles, which are responsible for the detection and initial transmission of sound. Finally, the inner ear contains the bony labyrinth, along with other structures essential for spatial orientation, hearing, and balance.
Non-insulinotropic diabetes medications are used to treat type 2 diabetes by methods other than increasing insulin secretion. This group of medications includes the biguanides, thiazolidinediones, alpha-glucosidase inhibitors, sodium–glucose transport protein 2 inhibitors, and amylin analogs. Mechanisms of action vary, but they can include increasing peripheral insulin sensitivity, reducing glucagon release, inhibiting gluconeogenesis, slowing glucose absorption, and increasing satiety. Metformin is the initial medication of choice; others may be used as an alternative monotherapy or as adjunctive therapy. Most of these medications are not associated with severe hypoglycemia, except for amylin analogs or when medications are used in conjunction with other hypoglycemic agents.
Insulinotropic diabetes medications treat type 2 diabetes mellitus by increasing insulin secretion, which results in decreased glucose levels. The group of medications includes sulfonylureas, meglitinides, glucagon-like peptide-1 (GLP-1) receptor agonists, and DPP-4 inhibitors. The agents are usually used in combination with other therapies for diabetes management. Sulfonylureas and meglitinides are associated with weight gain, while GLP-1 agonists may provide the added benefit of weight loss. Other side effects vary between the drug classes. None of the medications should be used in the treatment of type 1 diabetes mellitus or diabetic ketoacidosis.
Endometrial hyperplasia (EH) is the abnormal growth of the uterine endometrium. This abnormal growth may be due to estrogen stimulation or genetic mutations leading to uncontrolled proliferation. Endometrial carcinoma (EC) is the most common gynecologic malignancy in the developed world, and it has several histologic types. Endometrioid carcinoma (known as type 1 EC) typically develops from atypical endometrial hyperplasia, is hormonally responsive, and carries a favorable prognosis. Other histologic types are known as type 2 EC; they tend to present at more advanced stages, are not hormonally responsive, and carry a far worse prognosis. Women with both EH and EC tend to present with postmenopausal or irregular menstrual bleeding. Diagnosis is histologic. Management most often involves progestin therapy, surgery, and adjuvant radiation therapy (for advanced disease).
Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. There are several forms of insulin, and they differ in their time of onset, peak effect, and duration. Insulin can be classified as fast acting, short acting, intermediate acting, or long acting. A combination of classes can be used to maintain glucose control throughout the day. Common adverse effects include hypoglycemia, weight gain after initiation of an insulin regimen, and local injection site changes.
Ovarian cancer is a malignant tumor arising from the ovarian tissue and is classified according to the type of tissue from which it originates. The 3 major types of ovarian cancer are epithelial ovarian carcinomas (EOCs), ovarian germ cell tumors (OGCTs), and sex cord-stromal tumors (SCSTs). By far, EOCs are the most common, tend to present in postmenopausal women with advanced disease, and carry a poor prognosis. On the other hand, OGCTs and SCSTs frequently affect younger women, tend to present earlier, and carry a better prognosis. Affected individuals are frequently asymptomatic, although they may present with nonspecific symptoms such as fatigue, increasing abdominal girth, GI symptoms, and pelvic pain. Moreover, if the tumor secretes hormones, abnormal bleeding may be a presenting symptom. Diagnosis is suspected based on imaging studies and confirmed with histologic examination. Treatment is primarily surgical and often with adjuvant chemotherapy.
Vertigo is defined as the perceived sensation of rotational motion while remaining still. A very common complaint in primary care and the ER, vertigo is more frequently experienced by women and its prevalence increases with age. Vertigo is classified into peripheral or central based on its etiology. Vertigo is a clinical diagnosis, differentiated through history and physical examination findings, most notably nystagmus. Further testing may be required in malignant cases. Management depends on the etiology but certain maneuvers such as the Epley maneuver can be diagnostic and therapeutic.
Anticonvulsant drugs are pharmacological agents used to achieve seizure control and/or prevent seizure episodes. Anticonvulsants encompass various drugs with different mechanisms of action including ion-channel (Na+ and Ca+2) blocking and GABA reuptake inhibition. Phenobarbital, phenytoin, carbamazepine, valproic acid, and ethosuximide are the 1st-generation antiseizure drugs. Anticonvulsant drugs generally have complicated pharmacokinetics, multiple drug interactions, and narrow therapeutic ranges compared with new-generation drugs.
The brachial plexus is a network of nerves that originate from the lower cervical and upper thoracic nerve roots. The causes of brachial plexopathies include traumatic injuries, birth-related injuries, iatrogenic procedures, neoplastic processes, and previous treatment with radiation. Patients present with sensory and motor deficits related to the site of the lesion and the nerves involved. Diagnosis is made based on clinical findings, imaging, and electrodiagnostic studies. Treatment is related to the underlying cause and may be medical or surgical.
The term “persistent vegetative state,” also called unresponsive wakefulness, describes the condition of individuals with severe anoxic brain injury who have progressed to a state of wakefulness without any meaningful response to their environment. A persistent vegetative state is distinguished from a coma in that individuals in a persistent vegetative state have intermittent sleep–wake cycles. The individual's eyes may be open and there may be some yawning, grunting, or other vocalizations. In both cases, the individual is alive, but the brain does not function fully. Persistent vegetative state is most commonly associated with anoxic brain injury due to cardiac arrest, trauma, metabolic causes, or infections. Diagnosis is made by fulfilling specific diagnostic criteria. Treatment is controversial and ethically challenging. Recovery of consciousness from a posttraumatic persistent vegetative state is unlikely after 12 months, while recovery from a nontraumatic persistent vegetative state after 3 months is exceedingly rare.
Guillain-Barré syndrome (GBS), once thought to be a single disease process, is a family of immune-mediated polyneuropathies that occur after infections (e.g., with Campylobacter jejuni). Typical GBS is characterized by acute monophasic neuromuscular paralysis, which is symmetric and ascending in progression. If the paralysis reaches the respiratory muscles, GBS can progress into respiratory failure, which requires prolonged hospitalization. Management is mostly supportive and may require either plasma exchange or IV immunoglobulin.
Trigeminal neuralgia (TN) is an often chronic and recurring pain syndrome involving the sensory distribution of the trigeminal nerve (cranial nerve (CN) V). The pain is typically unilateral and described as an acute, sharp, electric-shock–like pain involving the maxillary or mandibular areas and often associated with spasm of facial muscles. Trigeminal neuralgia occurs in multiple, short-acting episodes. Most cases are usually due to vascular compression of the trigeminal nerve, although secondary causes can be from aneurysms, neuromas, or other neurologic disorders. A detailed history is the hallmark for diagnosis. Neuroimaging with MRI is useful to determine the exact pathology involving the trigeminal nerve root. The 1st line of therapy is pharmacologic (carbamazepine). Other treatment options include botulinum toxin injections or surgical procedures in refractory cases.
Posterior cord syndrome (PCS) is an incomplete spinal cord syndrome affecting the dorsal columns, the corticospinal tracts (CSTs), and descending autonomic tracts to the bladder. Posterior cord syndrome is rare but has a diverse range of etiologies, including demyelinating disorders, degenerative spinal conditions, neoplastic causes, vascular abnormalities, and hereditary neurodegenerative disorders. Clinical symptoms include gait ataxia, paresthesias with loss of position and vibration sense, and urinary incontinence. The diagnosis is made clinically and with neuroimaging. Management addresses treatment of the underlying cause.
Ataxia-telangiectasia, also known as Louis-Bar syndrome, is a neurocutaneous syndrome, which involves multiple systems but mainly affects the neurological system. Ataxia-telangiectasia is an autosomal recessive genetic disorder caused by a mutation in the ATM gene (ATM serine/threonine kinase or the ataxia-telangiectasia mutated gene). Ataxia-telangiectasia presents with progressive ataxia, telangiectasias, extrapyramidal symptoms, dermatological manifestations, immune dysfunction, and progressive pulmonary disease. Diagnosis is based on clinical presentation and confirmed with neuroimaging and genetic testing. Management is supportive with symptom management. Prognosis is poor secondary to numerous complications.
Neurofibromatosis type 2 is a neurocutaneous disorder that can arise from mutations in the NF2 gene located in chromosome 22 and may be inherited in an autosomal dominant fashion or occur from de novo mutations. The main clinical features are bilateral vestibular schwannomas, intracranial/spinal meningioma, and intramedullary and extramedullary spinal tumors. Other features can include eye lesions such as cataracts, skin lesions, and peripheral neuropathy. Diagnosis is made clinically from history and examination and confirmed with MRI, molecular testing, and histopathology. Tumor surveillance and follow-up with screening of at-risk family members is recommended. Management includes surgical interventions, radiation therapy, and/or monoclonal antibody therapy with bevacizumab.
Neurofibromatosis type 1 (NF1), also known as phakomatosis, is a neurocutaneous disorder that is most commonly of autosomal dominant inheritance due to mutations in the NF1 gene. Neurofibromatosis type 1 presents a range of clinical manifestations with the most prominent features being various pigmented skin lesions called café au lait macules (CALMs), benign nerve-sheath tumors called neurofibromas, freckling of the inguinal and axillary regions, and iris hamartomas, referred to as Lisch nodules. At least half of the individuals with NF1 have learning disabilities. Neurofibromatosis type 1 may also cause osteodysplasia and malignant transformation of tumors. The diagnosis is based on the typical clinical presentation and can be confirmed with genetic testing. Management depends on the clinical presentation and may vary from surgical removal to chemotherapy/radiotherapy for tumors, occupational therapy and PT for motor impairments, treatment with growth hormone, and bracing in the case of bone abnormalities.
Idiopathic intracranial hypertension (IIH), also known as pseudotumor cerebri, is a clinical disorder that presents with symptoms due to increased intracranial pressure (ICP; ≥ 20 mm Hg) or CSF pressure (> 250 mm H2O), with no structural changes or other attributable causes. The condition is most commonly observed in obese women and after intake of certain drugs, such as growth hormones, tetracycline antibiotics, and high dosages of vitamin A. Classic manifestations include headache, vision loss or visual-field defects, and papilledema. Diagnosis is made by clinical exam, imaging, and lumbar puncture. Management is aimed at decreasing ICP and includes medication, therapeutic CSF removal, and shunting.
Syncope is a short-term loss of consciousness and loss of postural stability followed by spontaneous return of consciousness to the previous neurologic baseline without the need for resuscitation. The condition is caused by transient interruption of cerebral blood flow that may be benign or related to a underlying life-threatening condition. Syncope is not a distinct disease entity; rather, it is a symptom of another pathologic process, whether it be transient or a more established disease process. Syncope may be accompanied by other symptoms, such as light-headedness, sweating, palpitations, nausea, feeling warm or cold, and visual blurring. Workup includes a detailed history and physical examination, electrocardiography, echocardiography, provocative testing (tilt-table test), or imaging of the suspected culprit vasculature. In many cases, a definite etiology is not found. Management is based on the underlying cause and can include physical countermaneuvers, stopping offending drugs, volume resuscitation, blood transfusion, and/or cardiac or vascular interventions.
Antiviral agents against human herpesviruses (HHVs) include acyclovir, cidofovir, and foscarnet. Human herpesviruses are DNA viruses in the Herpesviridae family. Herpes simplex virus (HSV), varicella-zoster virus (VZV), cytomegalovirus (CMV), Epstein-Barr virus (EBV), and HHV-8 belong to the Herpesviridae family. Antivirals against the group generally act via inhibition of DNA polymerase. Acyclovir (the prototypical nucleoside analog) requires viral kinase for phosphorylation to become a triphosphate, which is incorporated in viral DNA. Cidofovir requires phosphorylation by host cellular kinase, which allows cidofovir to have activity against mutated viruses and become deficient in viral kinase. Foscarnet (a pyrophosphate analog) does not require phosphorylation. Nephrotoxicity is a shared adverse effect in the agents. Acyclovir can also cause obstructive crystalline nephropathy and foscarnet carries a risk of electrolyte abnormalities and seizures. The nephrotoxic effect of cidofovir can be reduced with IV saline and probenecid.
Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased ICP can lead to brain herniation and death if not treated promptly. Clinical presentation includes headache, drowsiness or altered level of consciousness, and papilledema. Diagnosis is suspected based on the clinical presentation and confirmed with urgent brain imaging. Immediate management includes measures to decrease ICP, medications including diuretics, and surgery.
Antivirals for hepatitis B include the nucleoside/nucleotide analogs, also known as nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs). Because of their similar chemical structure to nucleosides and nucleotides, NRTIs are able to integrate into viral DNA during the replication process. This process inhibits the function of viral RNA-dependent DNA polymerase, resulting in chain termination. All of these medications are administered orally and are excreted by the kidneys. Indications include chronic hepatitis B infection, and some (such as lamivudine) are also used for HIV. Adverse effects include GI symptoms, evidence of mitochondrial toxicity (such as lactic acidosis), and rebound infection upon discontinuation.
Intracerebral hemorrhage (ICH) refers to a spontaneous or traumatic bleed into the brain parenchyma and is the 2nd-most common cause of cerebrovascular accidents (CVAs), commonly known as stroke, after ischemic CVAs. Trauma, hypertension, vasculopathy, vascular malformations, tumors, coagulopathy, and hemorrhagic conversion of ischemic stroke may all be causative factors. Clinical presentation may vary depending on the size and location of the hemorrhage and may range from headache, neurologic signs and symptoms, and altered level of consciousness to coma. Treatment includes stabilization, stopping or reversing of anticoagulation, blood pressure control, monitoring in a neurologic ICU, and possible neurosurgical intervention. Intracerebral hemorrhage is associated with significant morbidity and mortality.
Diarrheagenic Escherichia coli is a strain of pathogenic bacteria that can cause intestinal infection. Transmission is often through the fecal–oral route via the consumption of contaminated food or water. Pathogenesis varies based on the strain, but it can include toxin production, invasion of the mucosal surface, and adhesion with alteration of enterocyte structure. Noninvasive disease tends to present with watery diarrhea, while invasive infections cause bloody diarrhea. The diagnosis can be established with PCR. Management generally consists of supportive therapy (fluids and electrolytes). Antibiotics are reserved for severe or persistent infections and are contraindicated with enterohemorrhagic E. coli because of the risk of hemolytic uremic syndrome.
Bone, while seemingly inert, is an active, growing, and changing part of the human body, in addition to being the body's primary calcium reservoir. In the correct homeostatic conditions, bone can remodel in response to damage, stress, or hormonal signaling (parathyroid hormone and calcitonin). Osteocytes located deep in the bone sense damage and signal bone-lining cells that will begin the process of remodeling. This process is vital not only for damage repair but also to adapt to a new environment and conditions.
Epidural hemorrhage (EDH) is an event characterized by bleeding into the epidural space between the dural layers of the meninges and the skull. The primary mechanism triggering bleeding is trauma (i.e., closed head injury), which causes arterial injury, most commonly middle meningeal artery injury. Epidural hemorrhage presents acutely, usually immediately (seconds to hours) following head trauma, with an altered level of consciousness that may span from a momentary loss of consciousness to coma. Diagnosis is based on clinical suspicion following head trauma and is confirmed with neuroimaging (i.e., noncontrast head CT). Management includes stabilization, stopping (possibly, the reversal) of all anticoagulants, monitoring in a neurologic ICU, and neurosurgical intervention.
To undergo fertilization, the sperm enters the uterus, travels towards the ampulla of the fallopian tube, and encounters the oocyte. The zona pellucida (the outer layer of the oocyte) deteriorates along with the zygote, which travels towards the uterus and eventually forms a blastocyst, allowing for implantation to occur. An ectopic pregnancy occurs if the zygote does not reach the uterus before the zona pellucida degrades.
Subdural hemorrhage (SDH) is bleeding into the space between the dural and arachnoid meningeal layers surrounding the brain. The most common mechanism triggering the bleeding event is trauma (e.g., closed head injury) causing a tearing injury to the extracerebral “bridging” veins, but rupture of small arteries within this space or intracranial hypotension may also be causative. Acute SDH presents, immediately following head trauma, with an altered level of consciousness that may span from a momentary loss of consciousness to coma, which makes it a potentially life-threatening condition. Chronic SDH may also occur, presenting with a more gradual neurologic deterioration. Diagnosis is based on clinical suspicion following head trauma and confirmed with neuroimaging (e.g., noncontrast head CT). Management includes stabilization, stopping (possibly reversing) all anticoagulants, monitoring in a neurologic ICU, and neurosurgical intervention.
Hyponatremia is defined as a decreased serum sodium (sNa+) concentration less than 135 mmol/L. Serum sodium is the greatest contributor to plasma osmolality, which is very tightly controlled via antidiuretic hormone (ADH) release from the hypothalamus and by the thirst mechanism. The basic pathophysiology of all etiologies of hyponatremia is an abnormal increase in total body water (TBW), which dilutes the total body sodium (TBNa+) concentration. The clinical presentation varies greatly, from asymptomatic to subtle cognitive deficits, seizures, and death. Management is guided by etiology, acuity, and duration of symptoms, usually involving oral fluid restriction or administration of IV fluids that contain Na. Sodium must be replaced slowly, as overly rapid correction of hyponatremia can lead to irreversible neurologic complications and death, known as the osmotic demyelination syndrome (ODS).
Subarachnoid hemorrhage (SAH) is a type of cerebrovascular accident (stroke) resulting from intracranial hemorrhage into the subarachnoid space between the arachnoid and the pia mater layers of the meninges surrounding the brain. Most SAHs originate from a saccular aneurysm in the circle of Willis but may also occur as a result of trauma, uncontrolled hypertension, vasculitis, anticoagulant use, or stimulant use. The most classic symptom is a sudden-onset (thunderclap) headache along with neck stiffness, vomiting, a decreased level of consciousness, and seizure. As with any stroke, focal neurologic deficits are commonly present, and rapid neurologic deterioration may ensue without prompt diagnosis and intervention. An SAH should be suspected in any person presenting with thunderclap headache and neurologic symptoms, and the diagnosis can be confirmed with neuroimaging or lumbar puncture (LP). Treatment consists of reversal of anticoagulation, control of blood pressure, and neurosurgical intervention to contain the bleed and/or relieve elevated intracranial pressure (ICP). Even with prompt neurosurgical intervention, SAH carries a high mortality rate.
Gametogenesis is the development of gametes from primordial germ cells. This process differs between the sexes. In males, spermatogenesis produces spermatozoa. In females, oogenesis results in an ovum. The process starts with the migration of primordial germ cells from the yolk sac to the gonadal ridge. Oogenesis starts during the embryonic and fetal periods, whereas spermatogenesis starts at puberty. However, the phases of gametogenesis are similar, with germ cells progressing through mitosis, meiosis I, meiosis II, and maturation. This process results in gametes that are haploid, with 23 chromosomes.
The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th‒11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. The spleen can also activate immune responses, produce antibodies, and function as a reservoir for platelet storage. There are 2 primary types of splenic tissue: red pulp, which contains dense fibrovascular networks for filtering the blood, and white pulp, which is primarily made up of lymphoid tissue surrounding the larger vessels. The spleen has a relatively weak capsule; thus, it can rupture more easily than other abdominal organs and lead to life-threatening hemorrhage.
Portal hypertension is increased pressure in the portal venous system. This increased pressure can lead to splanchnic vasodilation, collateral blood flow through portosystemic anastomoses, and increased hydrostatic pressure. There are a number of etiologies, including cirrhosis, right-sided congestive heart failure, schistosomiasis, portal vein thrombosis, hepatitis, and Budd-Chiari syndrome. Most individuals are asymptomatic until complications arise, including esophageal varices, portal hypertensive gastropathy, ascites, and hypersplenism. The diagnosis is clinical, but it can be supported by ultrasound findings (and hepatic venous pressure gradient measurement in unclear cases). Management requires treating the underlying etiology and managing the complications. This can include nonselective beta blockers to prevent bleeding from varices, diuretics and sodium restriction for ascites, and transjugular intrahepatic portosystemic shunt for refractory complications.
The peritoneum is a serous membrane lining the abdominopelvic cavity. This lining is formed by connective tissue and originates from the mesoderm. The membrane lines both the abdominal walls (as parietal peritoneum) and all of the visceral organs (as visceral peritoneum). The peritoneum supports and suspends the organs within the abdominal cavity and provides an important conduit for the neurovasculature supplying these organs. There are several peritoneal folds, known as mesenteries, omenta, and ligaments. The greater and lesser omenta divide the peritoneal cavity into greater and lesser sacs, which are important anatomic spaces within the cavity. Organs located behind the posterior parietal peritoneum are known as retroperitoneal, while organs that protrude into the cavity and are fully covered by visceral peritoneum are known as intraperitoneal.
Hepatitis C is an infection of the liver caused by the hepatitis C virus (HCV). Hepatitis C virus is an RNA virus and a member of the genus Hepacivirus and the family Flaviviridae. The infection can be transmitted through infectious blood or body fluids and may be transmitted during childbirth or through IV drug use or sexual intercourse. Hepatitis C virus can cause both acute and chronic hepatitis, ranging from a mild to a serious, lifelong illness including liver cirrhosis and hepatocellular carcinoma (HCC). Hepatitis C infection is diagnosed by testing for the presence of HCV antibodies and HCV RNA. Management is supportive but includes direct antiviral agents (DAAs) if infection does not resolve spontaneously.
Hepatitis B virus (HBV) is a partially double-stranded DNA virus, which belongs to the Orthohepadnavirus genus and the Hepadnaviridae family. Hepatitis B virus is transmitted by exposure to infectious blood or body fluids. Examples of types of exposure include sexual intercourse, IV drug use, and childbirth. The virus can cause potentially life-threatening liver disease. Most individuals with acute HBV infection are asymptomatic or have mild, self-limiting symptoms. Chronic infection can be asymptomatic or create hepatic inflammation, leading to liver cirrhosis and hepatocellular carcinoma (HCC). Management of acute hepatitis is typically supportive. Administration of antivirals or liver transplantation may be necessary in fulminant and chronic cases.
Genital herpes infections are common sexually transmitted infections caused by herpes simplex virus (HSV) type 1 or 2. Herpes simplex virus type 1 is more commonly associated with non-genital herpes, while HSV-2 is more commonly associated with genital herpes. Primary infection often presents with systemic, prodromal symptoms followed by clusters of painful, fluid-filled vesicles on an erythematous base, dysuria, and painful lymphadenopathy. Primary infection can also be asymptomatic. Herpes infections are unique in that the virus is able to remain dormant in the neuronal ganglia, which allows for recurrent infections. Recurrent outbreaks are usually less severe than the initial infection. Treatment is with antiviral therapy, primarily acyclovir.
Pseudomembranous colitis is a bacterial disease of the colon caused by Clostridium difficile. Pseudomembranous colitis is characterized by mucosal inflammation and is acquired due to antimicrobial use and the consequent disruption of the normal colonic microbiota. C. difficile infections account for the most commonly diagnosed hospital-acquired diarrheal illnesses. C. difficile infections can range from asymptomatic colonization to diarrhea and progress to fulminant colitis with systemic sepsis in severe cases. The diagnosis is established based on stool studies. Management of pseudomembranous colitis is mainly using antibiotics. Fecal transplant is considered in a few cases, whereas surgical intervention is required in severe cases.
The most common complications include pneumonia, respiratory failure and acute respiratory distress syndrome (ARDS), sepsis and septic shock, cardiomyopathy, acute kidney injury (AKI), and pulmonary thromboembolism. Other complications include acute stroke, arrhythmias, acute cardiac injury, and dermatologic manifestations.
Pituitary adenomas are tumors that develop within the anterior lobe of the pituitary gland. They are classified by size (either micro- or macroadenomas) and by their ability to secrete hormones. Non-functioning or non-secretory adenomas do not secrete hormones but can compress surrounding pituitary tissue, leading to hypopituitarism. Secretory adenomas secrete various hormones depending on the cell type from which they evolved, leading to hyperpituitarism.
Pleuritis, also known as pleurisy, is an inflammation of the visceral and parietal layers of the pleural membranes of the lungs. The condition can be primary or secondary and results in sudden, sharp, and intense chest pain on inhalation and exhalation. Etiologies include infection, trauma, cardiac ischemia, and lung cancer. The most common primary infectious cause is a viral infection, and underlying lung infections account for the majority of secondary infectious causes. Management consists of pain control and the treatment of the underlying condition.
Sinusitis refers to inflammation of the mucosal lining of the paranasal sinuses. The condition usually occurs concurrently with inflammation of the nasal mucosa (rhinitis), a condition known as rhinosinusitis. Acute sinusitis is due to an upper respiratory infection caused by a viral, bacterial, or fungal agent. Viral etiologies are the most common cause. Sinusitis presents with facial pain over the affected sinus and purulent rhinorrhea. Diagnosis is usually clinical and management is supportive, although it may require antibiotics.
Gestational trophoblastic diseases are a spectrum of placental disorders resulting from abnormal placental trophoblastic growth. These disorders range from benign molar pregnancies (complete and partial moles) to neoplastic conditions such as invasive moles and choriocarcinoma. Diagnosis is confirmed by elevated serum beta human chorionic gonadotropin (hCG) and ultrasound findings, which are dependent on the disorder. Treatment is primarily through dilation and curettage and/or methotrexate.
Pharyngitis is an inflammation of the back of the throat (pharynx). Pharyngitis is usually caused by an upper respiratory tract infection, which is viral in most cases. It typically results in a sore throat and fever. Other symptoms may include a runny nose, cough, headache, and hoarseness. Determining the causative agent based on symptoms alone is difficult. Thus, a throat swab is often performed to rule out a bacterial cause. The mainstay of treatment is symptomatic and supportive, with bacterial causes requiring antibiotics.
Congestive heart failure refers to the inability of the heart to supply the body with normal cardiac output to meet metabolic needs. Echocardiography can confirm the diagnosis and give information about the ejection fraction. Treatment is directed at the removal of excess fluid and decreasing oxygen demand of the heart. Prognosis depends on the underlying cause, compliance with medical therapy, and presence of comorbidities.
Ventricular fibrillation (VF or V-fib) is a type of ventricular tachyarrhythmia (> 300/min) often preceded by ventricular tachycardia. In this arrhythmia, the ventricle beats rapidly and sporadically. The ventricular contraction is uncoordinated, leading to a decrease in cardiac output and immediate hemodynamic collapse. Ventricular fibrillation is most commonly caused by underlying ischemic heart disease. It leads to death within minutes unless advanced cardiac life support measures are started immediately.
Granulomatosis with polyangiitis (GPA) is a rare autoimmune disease of unknown etiology. It leads to a necrotizing granulomatous inflammation of small and medium-sized blood vessels of the nose, sinuses, throat, lungs, and kidneys. Early stages of GPA often present with localized manifestations such as infections of the upper respiratory tract, skin lesions, and/or constitutional symptoms. Later stages can present with renal failure and severe respiratory disease. Early diagnosis and treatment of granulomatosis with polyangiitis (which involves the administration of corticosteroids and immunosuppressive agents such as methotrexate) may lead to a full remission but without treatment, the condition has a high mortality rate.
Malignant mesothelioma (usually referred to as simply "mesothelioma") is the malignant growth of mesothelial cells, most commonly affecting the pleura. The majority of cases are associated with occupational exposure to asbestos that occurred > 20 years before clinical onset, which includes dyspnea, chest pain, coughing, fatigue, and weight loss. Chest computed tomography (CT) scan shows multifocal pleural thickening and pleural effusion. Pleural biopsy is required for confirmation and to rule out metastases from lung or breast cancer. Treatment is rarely effective, with an average survival time of < 1 year.
Jaundice is the abnormal yellowing of the skin and/or sclera caused by the accumulation of bilirubin. Hyperbilirubinemia is caused by either an increase in bilirubin production or a decrease in the hepatic uptake, conjugation, or excretion of bilirubin. Etiologies often involve the liver and can be prehepatic, intrahepatic, or posthepatic. Other symptoms of hyperbilirubinemia include pruritus, pale stools, and darkened urine. The diagnosis is made based on liver function tests and imaging. Management is focused on treatment of the underlying condition.
Long QT syndrome (LQTS) is a disorder of ventricular myocardial repolarization that produces QT prolongation on electrocardiogram (ECG). Long QT syndrome is associated with an increased risk of developing life-threatening cardiac arrhythmias, specifically torsades de pointes. The condition may be congenital or acquired. Congenital LQTS is attributed to genetic mutations affecting cardiac ion channels. Acquired LQTS usually results from drug therapy and/or electrolyte abnormalities. Patients can be asymptomatic or present with palpitations, syncope, seizures, and even sudden cardiac death. Diagnosis is established with ECG along with medical and family history, laboratory workup, and other cardiac tests. Treatment is determined by etiology. Acquired LQTS requires removal of the offending drug and correction of electrolyte abnormalities. Congenital LQTS management involves avoidance of triggers of arrhythmia, intake of beta-blockers, and placement of an implantable cardioverter-defibrillator (ICD).
Crohn's disease is a chronic, recurrent condition that causes patchy transmural inflammation that can involve any part of the gastrointestinal tract. It is a type of inflammatory bowel disease (IBD) along with ulcerative colitis (UC). The terminal ileum and proximal colon are usually affected. Crohn's disease typically presents with intermittent, non-bloody diarrhea and crampy abdominal pain. Extraintestinal manifestations may include calcium oxalate renal stones, gallstones, erythema nodosum, and arthritis. Diagnosis is established via endoscopy with biopsy that shows transmural inflammation, characteristic “cobblestone” mucosa, and noncaseating granulomas. Management is with corticosteroids, azathioprine, antibiotics, and anti-TNF agents (infliximab and adalimumab). Complications include malabsorption, malnutrition, intestinal obstruction or fistula, and an increased risk of colon cancer.
Seborrheic dermatitis is a common chronic, relapsing skin disorder that presents as erythematous plaques with greasy, yellow scales in susceptible areas (scalp, face, and trunk). Seborrheic dermatitis has a biphasic incidence, occurring in two peaks: first in infants, then in adolescence and early adulthood. Although the exact etiology is unknown, pathologic mechanisms have been observed involving the sebaceous glands and Malassezia on the skin. Topical medications are used for acute exacerbation or maintenance treatment. These options aim to inhibit skin colonization (antifungal agents), reduce inflammation (steroids, calcineurin inhibitors), and loosen scales and crusts (keratolytic agents). Severe and refractory seborrheic dermatitis may warrant the use of systemic antifungal medications.
Friedreich's ataxia is an autosomal recessive disorder characterized by progressive spinocerebellar degeneration. It presents in the 1st to 2nd decades of life with progressive gait ataxia, weakness, tremor, dysarthria, dysphagia, hypertrophic cardiomyopathy, and/or diabetes. Patients eventually become bedridden. Diagnosis is confirmed by genetic testing showing trinucleotide repeat expansion in the FXN gene. Treatment is supportive and most patients die of heart disease in the 4th or 5th decade of life.
Neonatal polycythemia is a hematocrit (HCT) that is 2 standard deviations above the average values for gestation and postnatal age. Neonatal polycythemia can develop from increased fetal hematopoiesis (secondary to placental insufficiency, maternal endocrinopathies, genetic disorders, etc.) or passive erythrocyte transfusion (placental-, feto-, or maternal-fetal transfusion). Patients may be asymptomatic or present with plethora, cardiorespiratory distress, and other symptoms. Continuous monitoring of vital signs and metabolic derangements is important. Treatment includes partial exchange transfusion.
Cirrhosis is a late stage of hepatic parenchymal necrosis and scarring (fibrosis) most commonly due to hepatitis C infection and alcoholic liver disease. Patients may present with jaundice, ascites, and hepatosplenomegaly. Cirrhosis can also cause complications such as hepatic encephalopathy, portal hypertension, portal vein thrombosis, and hepatorenal syndrome. Diagnosis is clinical. Management requires treating the underlying disease, managing complications, and, if required, liver transplantation.
Thoracic aortic aneurysm (TAA) is the abnormal dilation of a segment of the thoracic aorta, usually the ascending aorta. Most TAAs are due to degenerative aortic disorders, commonly in patients > 65 years of age. Genetic TAAs account for 20% of cases and are frequently found in younger patients. Most TAAs are asymptomatic (incidentally found in imaging) but could present with symptoms from its effects on surrounding structures. Aortic rupture is a life-threatening emergency. Among diagnostic imaging studies, computed tomography (CT) angiography is the most widely utilized. In asymptomatic cases, aortic expansion is monitored. Operative repair is recommended for symptomatic TAAs and increasing aortic diameter (criteria varies with location and underlying condition).
Cor pulmonale is right ventricular (RV) dysfunction caused by lung disease that results in pulmonary artery hypertension. The most common cause of cor pulmonale is chronic obstructive pulmonary disease. Dyspnea is the usual presenting symptom. Clinical findings include signs of right-sided heart failure and hypoxemia. While right cardiac catheterization is the gold standard test, most patients are diagnosed clinically and through the use of noninvasive testing. Echocardiography shows RV enlargement and elevated pulmonary arterial systolic pressure. Management is first focused on the underlying disease. Oxygen therapy improves disease progression, while diuretics reduce RV filling pressure. Lung transplantation is an option for those refractory to therapy.
Congenital diaphragmatic hernias are embryologically derived defects in the diaphragm through which abdominal structures can pass into the chest cavity. The presence of intestines and intra-abdominal organs in the chest interferes with embryonic development of the lungs, which is the major cause of pathology postnatally. Prenatal diagnosis is commonly made by ultrasound during pregnancy followed by confirmation on chest X-ray after birth. Immediate respiratory resuscitation at birth with endotracheal intubation and mechanical ventilation are required. Surgical repair is the only curative option. Prognosis varies, but children with diaphragmatic hernias usually suffer from lifelong pulmonary complications.
The cubital fossa is the region anterior to the elbow joint. The cubital fossa is seen as the triangular depression between the brachioradialis and pronator teres muscles. Except for the ulnar nerve, which runs posteriorly, most of the major neurovascular structures transition from the arm to the forearm via the cubital fossa. The 4 important structures of the cubital fossa (from lateral to medial) are the radial nerve, tendon of the biceps brachii muscle, brachial artery, and median nerve.
Psoriasis is a common T-cell–mediated inflammatory skin condition. The etiology is unknown, but is thought to be due to genetic inheritance and environmental triggers. There are 4 major subtypes, with the most common form being chronic plaque psoriasis. Plaques are well-circumscribed and salmon-colored, with silvery scales. Plaques commonly appear on the scalp and extensor surfaces of the extremities. Diagnosis is clinical. Treatment options are determined by the percentage of body surface area (BSA) affected and include topical corticosteroids, retinoids, calcineurin inhibitors, disease-modifying antirheumatic drugs (DMARDs), biologics, and phototherapy.
Chronic pancreatitis is due to persistent inflammation, fibrosis, and irreversible cell damage to the pancreas, resulting in a loss of endocrine and exocrine gland function. The most common etiologies are alcohol abuse and pancreatic duct obstruction. Patients often present with recurrent epigastric abdominal pain, nausea, and features of malabsorption syndrome (diarrhea, steatorrhea, and weight loss). Characteristic computed tomography (CT) findings include pancreatic atrophy, dilated pancreatic ducts, and pancreatic calcifications. Therapy focuses on alcohol cessation, diet changes, pain management, and treatment of pancreatic insufficiency.
Tricuspid regurgitation (TR) is a valvular defect that allows backflow of blood from the right ventricle to the right atrium during systole. Tricuspid regurgitation can develop through a number of cardiac conditions that cause dilation of the right ventricle and tricuspid annulus. A blowing holosystolic murmur is best heard at the left lower sternal border. Mild TR may be asymptomatic or present with systemic venous congestion due to increased right atrial and venous pressures. Echocardiography can establish the diagnosis. Treatment focuses on heart failure management, and surgery is reserved for severe disease.
Listeria spp. are motile, flagellated, gram-positive, facultative intracellular bacilli. The major pathogenic species is Listeria monocytogenes. Listeria are part of the normal gastrointestinal flora of domestic mammals and poultry and are transmitted to humans through the ingestion of contaminated food, especially unpasteurized dairy products. Listeria can also infect the fetus in utero or neonates during vaginal birth. Healthy individuals exposed to L. monocytogenes usually do not become ill if the inoculum is small, or may develop only self-limiting gastroenteritis. Immunocompromised or elderly individuals, neonates, and pregnant women can develop invasive disease, including meningitis and bacteremia. Treatment of invasive listeriosis includes ampicillin and gentamicin.
Tricuspid stenosis (TS) is a valvular defect that obstructs blood flow from the right atrium to the right ventricle during diastole. This condition most commonly results from rheumatic heart disease or a congenital defect, and is usually found in conjunction with other valvular disease. A mid-diastolic murmur is best heard at the lower left sternal border. Mild TS may be asymptomatic or present with systemic venous congestion due to increased right atrial and venous pressures. Echocardiography can establish the diagnosis. Treatment focuses on heart failure management, and surgery is reserved for severe disease.
Renal artery stenosis (RAS) is the narrowing of one or both renal arteries, usually caused by atherosclerotic disease or by fibromuscular dysplasia. If the stenosis is severe enough, the stenosis causes decreased renal blood flow, which activates the renin-angiotensin-aldosterone system (RAAS) and leads to renovascular hypertension (RVH), which only accounts for a small fraction of all cases of hypertension. Renovascular hypertension can be associated with abdominal bruits, renal insufficiency, or progressive renal atrophy. Diagnosis is by clinical presentation followed by imaging studies, including duplex ultrasonography, magnetic resonance angiography (MRA), computed tomography angiography (CTA), and sometimes catheter-based angiography. Revascularization is usually reserved for cases in which medical therapy has failed.
Stevens-Johnson syndrome (SJS) is a cutaneous, immune-mediated hypersensitivity reaction that is commonly triggered by medications, including antiepileptics and antibiotics. The condition runs on a spectrum with toxic epidermal necrolysis (TEN) based on the amount of body surface area (BSA) involved. Stevens-Johnson syndrome is characterized by keratinocyte necrosis and separation of the epidermis from the dermis. Patients will present with a flu-like prodrome, followed by cutaneous bullae and sloughing on the face, thorax, and mucous membranes. Stevens-Johnson syndrome is considered a medical emergency, and management is largely supportive. Withdrawal of the causative agent is required. Monitoring for, and treating, superinfection is essential due to the high risk of associated death in these patients.
Valvular disorders can arise from the pulmonary valve, located between the right ventricle (RV) and the pulmonary artery (PA). Valvular disorders are diagnosed by echocardiography. Pulmonary stenosis (PS) is valvular narrowing causing RV outflow tract obstruction. Patients are often asymptomatic unless they have other congenital cardiac anomalies or severe PS. Symptoms (exertional dyspnea, chest pain, and syncope) are due to RV failure. Severe PS is treated surgically.
Neisseria is a genus of bacteria commonly present on mucosal surfaces. Several species exist, but only 2 are pathogenic to humans: N. gonorrhoeae and N. meningitidis. Neisseria species are non-motile, gram-negative diplococci most commonly isolated on modified Thayer-Martin (MTM) agar. These pathogens have many virulence factors, including fimbriae, lipooligosaccharide envelope proteins, a polysaccharide capsule (unique to N. meningitidis), and IgA protease. Gonococcal infections are sexually or perinatally transmitted and include gonorrhea, pelvic inflammatory disease, septic arthritis, and neonatal conjunctivitis. Meningococcal infections are transmitted via respiratory and oral secretions. They most commonly cause meningococcemia with petechial hemorrhages and meningitis.
Primary biliary cholangitis (PBC) is a chronic disease resulting in autoimmune destruction of the intrahepatic bile ducts. The typical presentation is that of a middle-aged woman with pruritus, fatigue, and right upper quadrant abdominal pain. Elevated liver enzymes and antimitochondrial antibodies (AMAs) establish the diagnosis. Medical management is limited to using ursodeoxycholic acid, a disease-modifying agent. Definitive treatment is liver transplantation, which is performed in late stages (cirrhosis).
Acute cholangitis is a life-threatening condition characterized by fever, jaundice, and abdominal pain which develops as a result of stasis and infection of the biliary tract. Septic shock, liver abscess, and multi-organ dysfunction are potential serious complications. The diagnosis is confirmed with ultrasound showing dilation of the common bile duct (CBD) or gallstones, elevated liver function tests, and leukocytosis. Treatment includes hemodynamic stabilization, broad-spectrum antibiotics, urgent biliary drainage, and cholecystectomy to prevent recurrence.
Atrioventricular (AV) block is a bradyarrhythmia caused by delay, or interruption, in the electrical conduction between the atria and the ventricles. Atrioventricular block occurs due to either anatomic or functional impairment, and is classified into 3 types. The 1st-degree block is due to delayed conduction through the AV node. The 2nd-degree block is characterized by progressive conduction delay or intermittently blocked conduction. The 3rd-degree block involves total interruption in conduction between the atria and ventricles, causing complete AV dissociation. Patients may be asymptomatic or may present with syncope, chest pain, dyspnea, and bradycardia depending on the severity of the block. Electrocardiography (ECG) establishes the diagnosis, and treatment is based on the type of block and hemodynamic stability of the patient.
Acute pancreatitis is an inflammatory disease of the pancreas due to autodigestion. Common etiologies include gallstones and excessive alcohol use. Patients typically present with epigastric pain radiating to the back. Diagnosis requires 2 of 3 criteria, including: characteristic abdominal pain, serum amylase and lipase 3 times the upper limit of normal, or characteristic radiology findings. Ranson’s criteria is commonly used to assess the severity. Management includes aggressive intravenous (IV) hydration, analgesia, nutritional support, and treatment of the underlying cause.
Gastroenteritis is inflammation of the stomach and intestines, commonly caused by infections from bacteria, viruses, or parasites. Transmission may be foodborne, fecal-oral, or through animal contact. Common clinical features include abdominal pain, diarrhea, vomiting, fever, and dehydration. Diagnostic testing with stool analysis or culture is not always required, but can help determine the etiology in certain circumstances. The majority of cases of gastroenteritis are self-limited; therefore, the only required treatment is supportive therapy (fluids). However, antibiotics are indicated in severe cases.
The most common benign liver tumors include hepatic hemangiomas, focal nodular hyperplasia, and hepatic adenomas. These tumors are mostly asymptomatic and/or found incidentally on abdominal imaging. While these tumors are benign, large lesions can cause symptoms such as upper abdominal pain, or produce complications such as bleeding. Malignant potential is a concern for hepatic adenoma, depending on risk factors. The diagnosis is based on imaging studies, with characteristic findings defining the tumor. Biopsy generally is reserved for equivocal cases. Management is observation for most small, asymptomatic, and non-growing tumors. However, high-risk factors, symptoms, increasing tumor size, and complications dictate the need for surgical intervention.
Hereditary angioedema (HAE), also known as C1 esterase inhibitor (C1-INH) deficiency, is an autosomal dominant disorder characterized by recurrent episodes of severe swelling (angioedema). Hereditary angioedema commonly affects the limbs, face, intestinal tract, and upper airway. Swelling in the airway can restrict breathing and lead to a life-threatening airway obstruction. Hereditary angioedema has 3 subtypes distinguished by their underlying etiologies and levels of C1 inhibitor in the blood. Management includes treatment with danazol, kallikrein inhibitors, and C1-INHs. Hereditary angioedema is self-limiting, but may be fatal if the airway becomes compromised.
Small bowel obstruction (SBO) is an interruption of the flow of the intraluminal contents through the small intestine, and is classified as mechanical (due to physical blockage) or functional (due to disruption of normal motility). The most common cause of SBO in the Western countries is post-surgical adhesions. Small bowel obstruction typically presents with nausea, vomiting, abdominal pain, distention, constipation, and/or obstipation. The diagnosis is established via imaging. Up to 80% of all cases will resolve with supportive management (bowel rest, intravenous (IV) hydration, and nasogastric decompression). However, surgery is required for persistent or complicated cases.
Fibromuscular dysplasia (FMD) is a nonatherosclerotic, noninflammatory, medium-sized angiopathy due to fibroplasia of the vessel wall. The condition leads to complications related to arterial stenosis, aneurysm, or dissection. The clinical presentation can differ depending on which arteries are affected, but may include secondary hypertension from renal artery stenosis (RAS), neurologic deficits from cerebrovascular involvement, claudication due to limb involvement, and intestinal angina from mesenteric artery disease. The diagnosis is confirmed with imaging, such as computed tomography with angiography. Treatment includes lifestyle modifications, antihypertensive therapy for RAS patients, and potential revascularization.
Dysphagia is the subjective sensation of difficulty swallowing. Symptoms can range from a complete inability to swallow, to the sensation of solids or liquids becoming “stuck.” Dysphagia is classified as either oropharyngeal or esophageal, with esophageal dysphagia having 2 sub-types: functional and mechanical. Common causes of functional dysphagia include achalasia, scleroderma, and diffuse esophageal spasm (DES). Mechanical causes of dysphagia include esophageal rings, webs, strictures, and cancer. Oropharyngeal dysphagia may be due to structural abnormalities or abnormal neuromuscular function and coordination. The diagnostic workup depends on the patient’s presenting symptoms, but may include manometry, barium esophagram, or direct visualization with nasopharyngeal laryngoscopy or endoscopy. Treatment varies depending on the underlying cause.
Large bowel obstruction is an interruption in the normal flow of intestinal contents through the colon and rectum. This obstruction may be mechanical (due to the actual physical occlusion of the lumen) or functional (due to a loss of normal peristalsis, also known as pseudo-obstruction). Malignancy and volvulus are the most common causes of mechanical large bowel obstruction. Typical symptoms include intermittent lower abdominal pain, abdominal distention, and obstipation. Diagnosis is established with imaging. Mechanical large bowel obstruction requires surgery in most cases.
Colorectal cancer (CRC) is the 2nd-leading cause of cancer-related death in the United States. Almost all cases of CRC are adenocarcinoma and the majority of lesions come from the malignant transformation of an adenomatous polyp. As most CRCs are asymptomatic, screening is essential in detecting early disease. Screening is recommended to start at the age of 45 years, utilizing various screening tools available with colonoscopy, flexible sigmoidoscopy, and fecal tests among them. For high-risk individuals, earlier and more frequent screening is recommended. Other stool-based strategies and visualization tests are also available for CRC screening.
Shigella is a genus of gram-negative, non-lactose-fermenting facultative intracellular bacilli. Infection spreads most commonly via person-to-person contact or through contaminated food and water. Humans are the only known reservoir. Because it is resistant to acid, Shigella spp. survive transit through the stomach; thus, only a small amount of inoculum is needed to cause disease. Shigellosis (Shigella dysentery) results in fever, abdominal pain, and bloody diarrhea, which are effects of the toxins and epithelial-cell invasion of the organism. In the majority of cases, symptoms resolve within a few days. However, complications of dehydration, hemolytic uremic syndrome, toxic megacolon, or reactive arthritis can arise. Treatment is primarily using fluid and electrolyte replacement and antibiotics.
Cardiac myxoma is the most common of the primary tumors of the adult heart, all of which are very rare. Cardiac myxoma is a benign neoplasm that arises from primitive multipotent mesenchymal cells. Most occur sporadically, but some are a part of some familial syndromes. All 4 chambers may give rise to myxoma, but 90% originate and grow in the atria, with a left-to-right ratio of approximately 4:1. Diagnosis is made by echocardiography, cardiac magnetic resonance imaging (MRI), or cardiac computed tomography (CT). Complete surgical excision is required because of the substantial risk of embolization and cardiovascular complications, including sudden death.
The human immunodeficiency virus (HIV) is a species of Lentivirus, a genus of the family Retroviridae, which causes HIV infections and acquired immunodeficiency syndrome (AIDS). The virus has high genetic variability and is divided into 2 major types, HIV type 1 (HIV-1) and HIV type 2 (HIV-2). The human immunodeficiency virus is a single-stranded, positive-sense, enveloped RNA virus, which targets and destroys WBCs, leading to frequent opportunistic infections and, eventually, death.
Chiari malformations (CMs) are a group of central nervous system (CNS) conditions characterized by the underdevelopment of the posterior cranial fossa with subsequent protrusion of neural structures through the foramen magnum. There are 4 types of CM, with type I being the most common. Headaches are the most common symptom. Diagnosis is made by clinical findings and confirmed by magnetic resonance imaging (MRI). Treatment is surgical, based on decompression of the posterior fossa and restoration of CNS flow. Prognosis depends on the type of malformation.
Vibrio is a genus of comma-shaped, gram-negative bacilli. It is halophilic, acid labile, and commonly isolated on thiosulfate-citrate-bile-sucrose (TCBS) agar. There are 3 clinically relevant species. Vibrio cholerae (V. cholerae) is found in brackish and marine waters. Vibrio cholerae is associated with cholera, which causes severe, secretory “rice-water” diarrhea. The other 2 species are Vibrio vulnificus (V. vulnificus) and Vibrio parahaemolyticus (V. parahaemolyticus), which are transmitted through raw or undercooked shellfish and are associated with wound infections, septicemia, and diarrhea.
Atrial septal defects (ASDs) are benign acyanotic congenital heart defects characterized by an opening in the interatrial septum that causes blood to flow from the left atrium (LA) to the right atrium (RA) (left-to-right shunt). Atrial septal defects account for approximately 15% of all cases of congenital heart disease (CHD), making ASDs the 2nd most common CHD. There are 4 types of ASD based on the location of the defect along the atrial septum, but the most common is the ostium secundum defect. Atrial septal defects are usually detected during a routine physical examination and confirmed by an echocardiogram. In infancy, most small ASDs close spontaneously by 2 years of age. Only patients that are symptomatic require surgical closure. In general, most patients with ASD can expect a good overall outcome.
Airway obstruction is a partial or complete blockage of the airways that impedes airflow. An airway obstruction can be classified as upper, central, or lower depending on location. Lower airway obstruction (LAO) is usually a manifestation of chronic disease, such as asthma or chronic obstructive pulmonary disease (COPD). Upper airway obstruction (UAO) and central airway obstruction (CAO) refers to a mechanical blockage of the large airways and are potentially life-threatening events, which need to be recognized and managed promptly.
Reactive arthritis is a seronegative autoimmune spondyloarthropathy that occurs in response to a previous gastrointestinal (GI) or genitourinary (GU) infection. The pathophysiology of this disease is unclear, but a significant proportion of affected patients are positive for HLA-B27. The disease manifests as asymmetric oligoarthritis (particularly of large joints in the lower extremities), enthesopathy, dactylitis, and/or sacroiliitis. Ocular, mucocutaneous, GI, GU, and cardiac manifestations may also occur. The diagnosis is clinical, and efforts should be made to rule out alternative diagnoses. Management focuses on controlling symptoms, typically with nonsteroidal anti-inflammatory drugs. An active infection should also be treated, particularly Chlamydia trachomatis.
Splenic rupture is a medical emergency that carries a significant risk of hypovolemic shock and death. Injury to the spleen accounts for nearly half of all injuries to intra-abdominal organs. The most common reason for a rupture of the spleen is blunt abdominal trauma, specifically, motor vehicle accidents. For individuals with splenomegaly, however, even minimal trauma may result in splenic injury or rupture. Patients often present with LUQ abdominal pain; however, pain may be referred to the left shoulder. Patients are at risk for hemodynamic instability due to blood loss. The diagnosis is generally made with CT imaging, and management, ranging from observation to splenectomy, depends on the patient’s hemodynamic stability.
Clostridia species comprise a group of spore-forming, obligate anaerobic, gram-positive bacilli. Major pathogenic species include Clostridium perfringens (C. perfringens), which is associated with gas gangrene; Clostridioides difficile, which is associated with pseudomembranous colitis; C. tetani, which causes tetanus; and C. botulinum, which causes botulism. Clostridium perfringens (C. perfringens), Clostridioides difficile, C. tetani, and C. botulinum have broad-spectrum invasiveness and clinical manifestations that are summarized below. Note that Clostridium difficile has been reclassified as Clostridioides difficile. However, exams will likely not have the updated genus for several years.
Benign prostatic hyperplasia (BPH) is a condition indicating an increase in the number of stromal and epithelial cells within the prostate gland (transition zone). Benign prostatic hyperplasia is common in men > 50 years of age and may greatly affect their quality of life. The development of BPH involves modifiable and non-modifiable risk factors, which lead to anatomic obstruction and downstream effects on other organ systems. Clinically, patients present with a combination of obstructive and bladder storage symptoms. Diagnosis is made by determining the severity of voiding symptoms through a variety of non-invasive (voiding diary, history, physical examination) and invasive (cystoscopy, urodynamics, transrectal ultrasound imaging) tools. Treatment is multimodal with medical and surgical components (prostatectomy) utilized in combination.
The apophysis is a secondary ossification center found on non-weight-bearing segments of bones. The apophysis is also the site of ligament or tendon insertion and is involved in the peripheral growth of the bone. These secondary growth centers are generally open in late childhood and may not close until early adulthood. With overuse, the apophysis may become inflamed and painful, becoming vulnerable to tearing and avulsion. An acute apophyseal avulsion fracture occurs when a portion of the apophysis is pulled off by the ligament, usually secondary to explosive movements and eccentric muscular contractions. Apophyseal avulsion fractures are primarily treated conservatively, but may require surgical repair if the avulsed fragment is large or significantly displaced.
The bones of growing children exhibit unique characteristics, which, combined with the unique mechanisms of injury seen in children, result in fracture patterns differing significantly from those common in adults. The greenstick fracture is an incomplete fracture usually seen in long bones. The bone is typically bent, and the fracture extends only partway through the bone. Greenstick fractures are at high risk for refracture and should be completely immobilized. Greenstick fractures rarely require reduction but should be managed cautiously to prevent malunion or angulation deformities. A patient with a greenstick fracture should be referred for orthopedic follow-up.
A “toddler’s fracture” is a spiral or oblique fracture of the distal tibia in toddlers resulting from a low-energy trauma with a rotational/twisting component. These fractures are often seen in children who are learning to walk and who do not have a specific history of trauma. The child can sometimes present with a painful limp or refusal to bear weight on the affected limb. Management comprises analgesia and immobilizing the injured leg for several weeks.
Antiretroviral therapy (ART) targets the replication cycle of the human immunodeficiency virus (HIV) and is classified based on the viral enzyme or mechanism that is inhibited. The goal of therapy is to suppress viral replication to reach the outcome of undetected viral load. Currently, reverse transcriptase, protease, integrase, and entry inhibitors are used in combined ART (cART) regimens. Combination therapy (3-drug regimen) is used to prevent drug resistance and cross-resistance, which develop through genetic mutations.
The bones of growing children exhibit unique characteristics. These characteristics, combined with the unique mechanisms of injury seen in children, result in fracture patterns that differ significantly from those that are common in adults. When axial loads are applied, particularly to long bones in children, compressive forces may result in buckling of the bone without disruption of the periosteum. These fractures are called buckle or torus fractures and are considered generally stable, requiring only immobilization.
Vascular rings are a group of rare malformations featuring congenital abnormalities of the aortic arch. The aberrant arteries often form a ring around the esophagus and trachea, putting pressure on these structures. Clinical symptoms range from stridor, respiratory distress, and/or dysphagia in neonates, to asymptomatic forms, noted incidentally in adults. Diagnosis is confirmed through X-ray and echocardiography, but may be further defined with a computed tomographic (CT) scan. Definitive treatment is surgical, and the prognosis is excellent as clinical recovery is immediate.
Salmonellae are gram-negative bacilli of the family Enterobacteriaceae. Salmonellae are flagellated, non-lactose-fermenting, and hydrogen sulfide-producing microbes. Salmonella enterica, the most common disease-causing species in humans, is further classified based on serotype as typhoidal (S. typhi and paratyphi) and nontyphoidal (S. enteritidis and typhimurium). Transmission occurs through the fecal-oral route and consumption of contaminated foods and water. Bacteria penetrate the intestinal cells through microfold cells of Peyer’s patches and cause abdominal symptoms. Pathogens can also disrupt sodium and chloride transport in the intestine (causing diarrhea) and invade the bloodstream (causing sepsis and nonintestinal infection). Major clinical presentations include typhoid or enteric fever, foodborne enterocolitis, and bacteremia. Antibiotic treatment is considered in severe illness and chronic carrier states.
Hashimoto's thyroiditis, or chronic lymphocytic thyroiditis, is the most common cause of hypothyroidism in iodine-sufficient regions. The condition is an autoimmune disorder leading to destruction of the thyroid cells and thyroid failure. The gradual clinical course of Hashimoto's thyroiditis starts with a transient hyperthyroid state (“hashitoxicosis”) followed by subclinical hypothyroidism. Eventually, progression to overt hypothyroidism occurs, which is permanent. Patients may have a painless goiter, but in later stages, the gland is atrophic. Diagnosis is by laboratory tests showing elevated thyroid-stimulating hormone (TSH), low free thyroxine (T4), and positive antibodies against thyroglobulin and thyroid peroxidase. In uncertain cases, imaging is required. Radioactive iodine uptake will show low iodine uptake and ultrasound demonstrates diffuse symmetric enlargement. Biopsy shows lymphocytic infiltration with Hurthle cells. Treatment is lifelong thyroid hormone replacement.
Graves' disease is an autoimmune disorder characterized by the presence of circulating antibodies against the thyroid-stimulating hormone (TSH) receptors, thereby causing the thyroid gland to hyperfunction. Clinical features include hyperthyroidism (of which Graves' disease is the most common cause), orbitopathy, goiter, and dermopathy/pretibial myxedema. Manifestations reflect the muti-systemic effects of a hyperactive thyroid, including heat intolerance, sweating, palpitations, tremors, pretibial myxedema, and exophthalmos. Diagnosis is by thyroid laboratory tests showing a low TSH, elevated thyroid hormones (thyroxine (T4) and triiodothyronine (T3)) and thyrotropin-receptor antibodies (particularly the thyroid-stimulating immunoglobulins subtype). If initial tests are nondiagnostic, radioactive iodine uptake (increased uptake) and thyroid ultrasound (diffuse thyroid enlargement) provide diagnostic information. Treatment options include thionamides, radioiodine ablation, and surgery.
Chlamydial infections are a group of infectious diseases caused by bacteria belonging to the Chlamydiaceae family. The 3 species that can infect humans are Chlamydia trachomatis, C. pneumoniae, and C. psittaci. The most common infection is an STI caused by C. trachomatis, which affects the genitourinary tract. Chlamydia is the most common sexually transmitted bacterial infection in the United States. Other species of Chlamydia mainly cause respiratory infections. Diagnosis is based on nucleic acid amplification tests. Management is with antibiotics. Untreated chlamydial infections may have serious consequences, including sterility, ectopic pregnancies, spontaneous abortions, and chronic pelvic inflammatory disease.
Polymyositis (PM) is an autoimmune inflammatory myopathy caused by T cell-mediated muscle injury. The etiology of PM is unclear, but there are several genetic and environmental associations. Polymyositis is most common in middle-aged women and rarely affects children. Patients present with progressive and symmetric proximal muscle weakness and constitutional symptoms. Complications may arise from respiratory, cardiac, or GI involvement. Diagnosis is based on clinical presentation and laboratory studies and confirmed using muscle biopsy. Management is with systemic glucocorticoids, immunosuppressants, and physiotherapy. All patients should undergo cancer screening because there is a strong association with malignancy.
IgA nephropathy (Berger's disease) is a renal disease characterized by IgA deposition in the mesangium. It is the most common cause of primary glomerulonephritis in most developed countries. Patients frequently present in the second and third decades of life and, historically, with a preceding upper respiratory or GI infection. Common presenting features are gross hematuria or asymptomatic, microscopic hematuria on urinalysis. The course is often benign, with the definitive diagnostic procedure, renal biopsy, performed only in cases of severe, progressive renal disease. Treatment depends on the severity of proteinuria, renal function, and pathologic changes. ACE inhibitors or angiotensin-receptor blockers (ARBs) are given to reduce disease progression. Persistent proteinuria and increasing creatinine are indications for immunosuppressive therapy that includes glucocorticoids and, possibly, cytotoxic agents.
Sick sinus syndrome (SSS), also known as sinus node dysfunction, is characterized by degeneration of the sinoatrial (SA) node, the heart’s primary pacemaker. Patients with SSS may be asymptomatic or may present with tachycardia or bradycardia. In cases of bradycardia, patients can experience fatigue, light-headedness, and syncope. Diagnosis is made by physical exam and ECG. Management can include a pacemaker.
Supracondylar fractures are the most common elbow fractures in the pediatric population. The most common mechanism of injury involves a fall on an outstretched hand, resulting in a fracture of the distal humerus. Patients frequently present with pain, visible deformity, and limited range of motion of the injured elbow. This fracture often requires immediate orthopedic consultation secondary to the displacement of the fracture and the frequency of concomitant neurovascular injury.
Rosacea is a chronic inflammatory disease of the skin that is associated with capillary hyperreactivity. This condition is predominantly seen in middle-aged women, and is more common in fair-skinned patients. Patients may have facial erythema, flushing, telangiectasia, papules, pustules, phymatous changes, and ocular manifestations. The diagnosis is clinical. Management includes avoidance of triggers, gentle skincare, topical (and/or oral) antibiotics, and laser (or surgical) therapies.
Dilated cardiomyopathy (DCM) is the most common type of non-ischemic cardiomyopathy and a common cause of heart failure (HF). The cause may be idiopathic, familial, or secondary to a variety of underlying conditions. The disease is characterized by the enlargement of 1 or both ventricles and reduced systolic function. Patients typically present with symptoms of HF such as shortness of breath, fatigue, weakness, and peripheral edema. Blood tests, ECG, X-rays, echocardiography, and other cardiac studies and procedures are typically done to obtain the diagnosis. Treatment includes medications used to reduce volume overload (e.g., diuretics) and manage HF (e.g., beta-blockers). Devices such as pacemakers and cardioverter-defibrillators may also be needed. In severe cases, a heart transplant is required. Complications include thromboembolic events and sudden cardiac death.
Becker muscular dystrophy (BMD) is an X-linked recessive genetic disorder that is caused by a mutation in the DMD gene. Abnormal, partially functional muscle dystrophin protein is produced, which leads to progressive muscle weakness and the eventual loss of ambulation. The clinical course is highly variable, but symptoms generally occur by adolescence. The diagnosis is based on muscle enzymes, genetic testing, and muscle biopsy (if necessary). Management of BMD is supportive and aimed at slowing disease progression and complications. Dilated cardiomyopathy is the leading cause of death.
A thyroid nodule is a disordered growth of thyroid cells that produces a mass in the thyroid gland. Most thyroid nodules are benign and detected either by the patient or by the clinician on examination. In other cases, a thyroid nodule is found in radiologic imaging incidentally. Ruling out of malignancy is important. Workup includes thyroid-stimulating hormone (TSH) and thyroid ultrasound followed by radioactive iodine (RAI) uptake scan or thyroid scan if initial tests suggest the presence of hyperthyroidism. Fine-needle aspiration biopsy (FNAB) is recommended in patients with suspicious ultrasound findings, "cold" nodules (iodine uptake < surrounding tissue) on thyroid scan, large nodules (generally > 1.5 cm), or risk factors for malignancy. Management is dictated by pathology findings and can range from periodic ultrasound monitoring to surgery.
Lentigo maligna is melanoma in situ, a precancerous lesion that may progress to an invasive melanoma (specifically lentigo maligna melanoma subtype). This condition typically occurs in sun-damaged areas (e.g., face and neck) of elderly patients. Lentigo maligna presents as a brown macule with color variegation and asymmetrical borders that grow slowly. The lesion should be biopsied to confirm a diagnosis and surgical excision with a safety margin is the 1st-line treatment.
Dermatomyositis (DM) is an autoimmune and inflammatory myopathy. Although the etiology of DM is unclear, it has several genetic and environmental associations. Dermatomyositis is common in women around the age of 50 years. Patients present with symmetrical, proximal weakness, characteristic skin manifestations, and systemic symptoms. Diagnosis is based on clinical presentation and laboratory studies and confirmed on the basis of muscle biopsy. Myositis-specific antibodies, including anti-Mi-2, are specific markers in DM. Management is with systemic glucocorticoids, immunosuppressants, and physiotherapy. As there is a strong association of DM with malignancy, all patients should undergo cancer screening.
Cellulitis is a common infection caused by bacteria that affects the dermis and subcutaneous tissue of the skin. It is frequently caused by Staphylococcus aureus and Streptococcus pyogenes. The skin infection presents as an erythematous and edematous area with warmth and tenderness. The borders are not clearly delineated. The lower extremities are the most frequent site of infection, but cellulitis can occur anywhere on the body. Diagnosis is usually clinical, and management involves oral and/or parenteral antibiotics. Coverage for MRSA may be added, depending on the presence of risk factors.
Adenomyosis is a benign uterine condition characterized by the presence of ectopic endometrial glands and stroma within the myometrium. Adenomyosis is a common condition, affecting 20%–35% of women, and typically presents with heavy menstrual bleeding and dysmenorrhea. Diagnosis is often made with pelvic imaging. Usually, transvaginal ultrasound is adequate, though MRI can be helpful in indeterminate cases. Management is based on the patient’s preference regarding future childbearing and may include hysterectomy (definitive treatment), other surgical options, or medical hormonal suppression (usually with progestins).
Carotid artery stenosis is a chronic atherosclerotic disease resulting in narrowing of the common and internal carotid arteries. Common risk factors include family history, advanced age, hyperlipidemia, smoking, and diabetes mellitus. Patients may present with or without symptoms of decreased cerebral perfusion. Carotid artery stenosis is commonly diagnosed via ultrasound. Management includes lifestyle modifications to control progression of atherosclerosis. Treatment is with statins, anti-hypertensive and antiplatelet agents, and, in some cases, surgical revascularization. The most serious complication of carotid artery stenosis is stroke.
Thrombotic thrombocytopenic purpura (TTP) is a life-threatening condition due to either a congenital or an acquired deficiency of ADAMTS-13, a metalloproteinase that cleaves multimers of von Willebrand factor (VWF). The large multimers then aggregate excessive platelets resulting in microvascular thrombosis and an increase in consumption of platelets. Clinical presentation can consist of thrombocytopenia, hemolytic anemia, hematuria, gastrointestinal symptoms, neurological symptoms, and renal involvement. Diagnosis is established based on a combination of clinical symptoms and laboratory tests. Thrombotic thrombocytopenic purpura is a medical emergency and almost always fatal if appropriate treatment is not initiated promptly. Emergency management includes plasma exchange and immunosuppressive therapies.
Secondary amenorrhea is defined as the absence of menses for 3 months in a woman with previously regular menstrual cycles or for 6 months in a woman with previously irregular cycles. Etiologies involve either disruptions to the hypothalamic–pituitary–ovarian (HPO) axis or acquired obstructions in the uterus or outflow tract. The most common cause of secondary amenorrhea is pregnancy. The most common pathologic etiologies include functional hypothalamic amenorrhea, polycystic ovary syndrome, hyperprolactinemia, premature ovarian insufficiency, and Asherman's syndrome. The diagnosis is made with a thorough history and physical examination, measurement of hormone levels, a pregnancy test, and imaging with pelvic ultrasonography. A progestin and/or combined estrogen–progestin challenge can help further identify the location of the abnormality. Management depends on the underlying etiology, clinical presentation, and patient desires regarding fertility. Treatment can include lifestyle, medical, and surgical management options.
Acne vulgaris, also known as acne, is a common disorder of the pilosebaceous units in adolescents and young adults. The condition occurs due to follicular hyperkeratinization, excess sebum production, follicular colonization by Cutibacterium acnes, and inflammation. Acne can present as open or closed comedones, papules, pustules, nodules, or cysts. The diagnosis is based on clinical exam. Management depends on the severity, but includes skin care techniques, topical therapies, antibiotics, and retinoids.
Amyloidosis is a disease caused by abnormal extracellular tissue deposition of fibrils composed of various misfolded low-molecular-weight protein subunits. These proteins are frequently byproducts of other pathological processes (e.g., multiple myeloma). These misfolded proteins can become deposited in different tissues, interfere with normal organ functions, and cause tissue-specific diseases (e.g., renal amyloidosis causes proteinuria). Diagnosis is established clinically and confirmed with tissue biopsy. Treatment should be directed toward the underlying cause and the reduction of amyloid deposition.
Basal cell carcinoma is the most common skin malignancy. This cancer arises from the basal layer of the epidermis. The lesions most commonly appear on the face as pearly nodules, often with telangiectatic blood vessels and ulceration in elderly individuals. Diagnosis is established by tissue biopsy. Despite having low metastatic potential, basal cell carcinoma should be treated adequately because it is locally aggressive and destructive to tissues. Complete surgical excision is the main treatment method. Long-term prognosis is excellent with adequate management.
Chancroid is a highly transmissible STD caused by Haemophilus ducreyi. The disease presents with painful ulcer(s) on the genital tract (termed chancroid or “soft chancre”). Up to 50% of patients will develop painful inguinal lymphadenopathy. Furthermore, of that percentage, 25% may develop complications of the suppurative lymph nodes. Given the growth of H. ducreyi on a special medium (often not readily available), chancroid is diagnosed based upon clinical appearance and tests to rule out both syphilis and herpes (the most common causes of genital ulcers). Although the disease can resolve spontaneously, antibiotics (azithromycin or ceftriaxone) are the treatment of choice. Treatment should involve both patients and their sexual contacts.
Staphylococcal scalded skin syndrome (SSSS), also known as Ritter disease and staphylococcal epidermal necrolysis, is a toxin-mediated condition caused by Staphylococcus aureus. The exfoliative toxin produced disseminates and cleaves desmoglein 1 in the epidermis, causing separation and detachment of the skin. SSSS most commonly affects young children. Prodromal symptoms precede diffuse cutaneous erythema, tenderness, bullae formation, and superficial desquamation. The mucous membranes are spared. The diagnosis is made clinically and can be confirmed with culture data (targeting possible primary infection sites) and biopsy. However, cultures of bullae are not useful. Antibiotics and supportive care should be initiated as soon as the diagnosis is suspected.
An embolus is an intravascular solid, liquid, or gaseous material that is carried by the blood to a site distant from its point of origin. Emboli of all types warrant immediate medical attention. The majority of emboli dislodge from a thrombus, forming a thromboembolus. Other less common nonthrombotic types of emboli are cholesterol, fat, air, amniotic fluid, and tumor emboli. The cause of the embolus depends on the type, as does the clinical presentation, diagnosis, and management of each embolic condition. Due to their effects on circulation, all emboli have the potential to result in end-organ failure and death.
Mycobacterium is a genus of the family Mycobacteriaceae in the phylum Actinobacteria. Mycobacteria comprise more than 150 species of facultative intracellular bacilli that are mostly obligate aerobes. Mycobacteria are responsible for multiple human infections including serious diseases, such as tuberculosis (M. tuberculosis), leprosy (M. leprae), and M. avium complex infections. While lungs are the most common site of infection, mycobacteria can colonize and infect other organ systems including the lymph nodes, skin, sinuses, eyes, ears, bones, CNS, and urinary tract.
Restrictive cardiomyopathy (RCM) is a fairly uncommon condition characterized by progressive stiffening of the cardiac muscle, which causes impaired relaxation and refilling of the heart during diastole, resulting in diastolic dysfunction and eventual heart failure. It most often occurs secondary to scarring, damage, and/or infiltration of the heart muscle, with amyloidosis being the most common cause. Infrequently, it may be idiopathic or inherited. Signs and symptoms include shortness of breath, low exercise tolerance, fatigue, and peripheral edema. Diagnosis is made through clinical suspicion and confirmed through ECG, X-ray, echocardiography, and cardiac MRI. Treatment includes medications for heart failure, implantable devices such as pacemakers and cardioverter–defibrillators, and heart transplantation in refractory cases.
In the context of acute or chronic kidney failure, renal function may diminish to a point at which it is no longer able to adequately support life. When this happens, renal replacement therapy is indicated. Renal replacement therapy refers to dialysis and/or kidney transplantation. Dialysis is a procedure by which toxins and excess water are removed from the circulation. Hemodialysis and peritoneal dialysis (PD) are the two types of dialysis, and their primary difference is the location of the filtration process (external to the body in hemodialysis versus inside the body for PD).
Hyperaldosteronism is defined as the increased secretion of aldosterone from the zona glomerulosa of the adrenal cortex. Hyperaldosteronism may be primary (resulting from autonomous secretion), or secondary (resulting from physiological secretion due to stimulation of the RAAS). Classically, hyperaldosteronism presents with hypertension, hypokalemia, and metabolic alkalosis, although recent studies have suggested that hypokalemia is less common than originally thought in primary hyperaldosteronism. Patients with hypertension who are treatment resistant and/or associated with hyperkalemia should be screened for hyperaldosteronism by determining their plasma aldosterone concentration and plasma renin activity. Confirmatory tests and an abdominal CT scan are required to conclusively diagnose primary hyperaldosteronism. Management involves the use of aldosterone receptor antagonists and surgical excision of any aldosterone-secreting tumors.
Bariatric surgery refers to a group of invasive procedures used to surgically reduce the size of the stomach to produce early satiety, decrease food intake (restrictive type) and/or alter digestion, and artificially induce malabsorption of nutrients (malabsorptive type). The ultimate goal of bariatric surgery is drastic weight loss. Bariatric surgery is currently the only modality that provides significant long-term weight loss in morbidly obese individuals and cures or significantly improves obesity-related complications. The 2 modalities currently in wide use are the Roux-en-Y gastric bypass and sleeve gastrectomy.
Hyperparathyroidism is a condition associated with elevated blood levels of parathyroid hormone (PTH). Depending on the pathogenesis of this condition, hyperparathyroidism can be defined as primary, secondary or tertiary. Primary hyperparathyroidism is an inherent disease of parathyroid glands associated with abnormal secretion of PTH. Secondary hyperparathyroidism results from abnormalities of calcium metabolism, which, if left untreated, can progress to tertiary hyperparathyroidism, which is associated with hypertrophy of the parathyroid gland and oversecretion of PTH even if the primary cause is eliminated. Diagnosis is based on biochemical parameters, which include serum PTH, calcium, and phosphate levels as well as urinary calcium. Management relies mostly on surgical parathyroidectomy for primary and tertiary hyperparathyroidism. Management of secondary hyperparathyroidism is focused on treatment of the underlying disease.
Seborrheic keratosis (SK) is the most common benign epithelial cutaneous neoplasm. The condition consists of immature keratinocytes. Seborrheic keratosis is the most common benign skin tumor in middle-aged and elderly adults and presents as a sharply demarcated, exophytic, skin lesion that may be tan or black and has a “stuck-on” appearance. Pruritus or pain can occur if these lesions become secondarily inflamed by trauma, especially if they are within the skin folds. Genetics are thought to play a role, but the pathogenesis is uncertain. The most common mutations involve two oncogenes: fibroblast growth factor receptor 3 (FGFR3) and PIK3CA. There is a familial predisposition to develop a high number of seborrheic keratoses. Treatment is not necessary, as this is a benign condition, but cryotherapy, curettage or electrodesiccation can be performed for discomfort or cosmetic concerns.
Thyroiditis is a catchall term used to describe a variety of conditions that have inflammation of the thyroid gland in common. It includes pathologies that cause an acute illness with severe thyroid pain (e.g., subacute thyroiditis and infectious thyroiditis) as well as conditions in which there is no clinically evident inflammation and the manifestations primarily reflect thyroid dysfunction or a goiter (e.g., painless thyroiditis and fibrous Riedel’s thyroiditis). The etiology of thyroiditis is varied and includes autoimmune inflammation (most common), bacterial or viral infection, and drug-induced reactions. The inflammation of the thyroid leads to a sequential pathologic process that can result in signs and symptoms of hyperthyroidism followed by signs and symptoms of hypothyroidism. The resulting damage can be temporary or permanent, and the treatment depends on the underlying cause.
Potassium is the main intracellular cation in all cells and is distributed unevenly between the intracellular fluid (98%) and extracellular fluid (2%). This large disparity is necessary for maintaining the resting membrane potential of cells, and explains why K+ balance is tightly regulated. The GI tract secretes 5%–10% of the absorbed K+ daily; however, the kidneys are responsible for 90%–95% of the overall K+ regulation. While most of the K+ is reabsorbed in the proximal tubules, the majority of regulation occurs in the principal and α-intercalated cells of the collecting ducts. The most important regulatory mechanisms include aldosterone, plasma K+ concentration, distal urinary flow rate, and the distal delivery of Na+ and water. Hyperkalemia and hypokalemia can result when K+ regulation is abnormal.
Short bowel syndrome is a malabsorptive condition most commonly associated with extensive intestinal resection for etiologies such as Crohn's disease, bowel obstruction, trauma, radiation therapy, and vascular insufficiency. The short length of bowel results in insufficient surface area for fluid and electrolyte absorption. Patients typically present with diarrhea, electrolyte abnormalities, and dehydration. Management options include antimotility agents, antisecretory agents, and total parenteral nutrition for patients who cannot maintain themselves with oral intake. Last-resort options include surgical intestinal lengthening procedures and small bowel transplant.
Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder affecting the neuromuscular junction and has a strong association with small cell lung carcinoma. Lambert-Eaton myasthenic syndrome affects the voltage-gated calcium channels at the presynaptic membrane. Presentation includes proximal muscle weakness and symptoms of autonomic dysfunction such as dry mouth and sluggish pupillary reflexes. Diagnosis includes nerve conduction studies/electromyography (EMG) and serum detection of antibodies. Management is mainly symptomatic with the use of potassium channel blockers and immunosuppressants. Prognosis is good for nonparaneoplastic LEMS but usually poor for paraneoplastic LEMS secondary to underlying malignancy.
Trichinellosis is an illness caused by infection with Trichinella. The most common causative parasite is Trichinella spiralis, which is usually found in pigs and transmitted to humans through the ingestion of undercooked meat. Once ingested, the parasite grows and matures within the intestinal walls. The adult forms mate, and the larvae produced spread through the bloodstream, reaching striated muscles. Symptoms occur during larval migration. Patients may have GI symptoms within a few weeks after consumption of the infected meat, and systemic symptoms such as fever, chills, myalgia, and periorbital edema may follow. Diagnosis can be made by serologic examination and confirmed by the presence of cysts or larvae in a muscle biopsy. Mild infections are self-limited, but systemic disease is managed with antiparasitic medications and corticosteroids. Infection can be prevented by proper meat handling and cooking techniques.
Basic surgical intervention in the thoracic cavity has the primary goal of alleviating any malady that mechanically affects the function of the heart and lungs, which can be secondary to underlying pathologies or, most commonly, trauma. Interventions such as tube thoracostomy and thoracentesis are performed to evacuate fluid, blood, or air that is occupying the thoracic cavity in order to restore thoracic negative pressure. When direct intervention to the heart and mediastinum is required, an emergency thoracotomy is performed. Once the immediate mechanical problems are addressed, more advanced reparative surgery involving heart, lungs, or mediastinal structures can then be performed as necessary.
The respiratory system is responsible for eliminating the volatile acid carbon dioxide (CO2), which is produced via aerobic metabolism. The body produces approximately 15,000 mmol of CO2 daily, which is the majority of daily acid production; the remainder of the daily acid load (only about 70 mmol of nonvolatile acids) is excreted through the kidneys. In the setting of hypoventilation, this acid load is not adequately blown off, and respiratory acidosis occurs. Renal compensation occurs after 3–5 days, as the kidneys attempt to increase the serum bicarbonate levels. Patients are often asymptomatic, or they may present with neuropsychiatric manifestations or mild dyspnea. Diagnosis is made with arterial blood gas measurement. Management involves treating the underlying etiology, stabilizing the patient, and avoiding respiratory sedatives.
"The respiratory system is responsible for eliminating the volatile acid carbon dioxide (CO2), which is produced via aerobic metabolism. The body produces approximately 15,000 mmol of CO2 daily, which is the majority of daily acid production; the remainder of the daily acid load (only about 70 mmol of nonvolatile acids) is excreted through the kidneys. When hypoventilation occurs, excess carbon dioxide is blown off and respiratory alkalosis develops. The kidneys respond by decreasing serum bicarbonate (HCO3–) through increased HCO3– excretion or decreased excretion of H+. Patients present with an increased respiratory rate, dyspnea, light-headedness and potentially psychologic symptoms. Diagnosis involves a thorough history, an exam, and an arterial blood gas measurement. Management focuses on addressing the underlying abnormalities, stabilizing patients in acute distress, and potentially a small dose of short-acting benzodiazepines.
Magnetic resonance imaging is a technique that utilizes magnetic fields and radiofrequency pulses to produce highly detailed images of the human anatomy. Magnetic resonance imaging can detect minute changes, reliably delineate lesions, and characterize vascular malformations. Soft tissues, such as abnormalities affecting non-bony structures, can be evaluated using MRI. Images can be obtained in most planes (commonly used are sagittal, coronal, and axial). Contrary to CT, MRI does not expose patients to ionizing radiation. There are some limitations of this imaging modality: MRI is expensive, time consuming, and not readily available in some centers. Additionally, patients with ferromagnetic implants or devices cannot be exposed to the MRI equipment, which has magnets. Contrast studies may result in renal complications; thus, the determination of renal function is necessary before using certain contrast agents.
Idiopathic pulmonary fibrosis is a specific entity of the major idiopathic interstitial pneumonia classification of interstitial lung diseases. As implied by the name, the exact causes are poorly understood. Patients often present in the moderate to advanced stage with progressive dyspnea and nonproductive cough. The diagnosis is made by characteristic imaging findings, pulmonary function testing that indicates restrictive lung disease, and (if necessary) lung biopsy. Options are limited for therapies to slow progression. Lung transplantation is the only curative intervention if the patient is a candidate for one.
Brain abscess is a life-threatening condition that involves the collection of pus in the brain parenchyma caused by infection from bacteria, fungi, parasites, or protozoa. The most common presentation is headache, fever with chills, seizures, and neurological deficits. Diagnosis is mainly based on imaging, as it is difficult to arrive at a definitive diagnosis based on clinical presentation alone. Management includes administration of empiric antibiotic therapy and surgical intervention. Immediate management is necessary; otherwise, severe neurologic complications ensue.
Taenia belong to the Cestoda class of helminths. Humans are infected with these tapeworms by eating undercooked beef (T. saginata) or pork (T. solium and T. asiatica). Taeniasis is often asymptomatic, but the ingestion of larvae can cause abdominal discomfort, nausea, and constipation or diarrhea. Passing proglottids in the stool is the most common sign of taeniasis. A patient who ingests T. solium eggs can develop cysticercosis, which may present with muscular and dermatologic cysts, ocular involvement, or neurologic manifestations (neurocysticercosis). The diagnosis is made by identifying proglottids or eggs in the stool. Characteristic findings on CT or MRI will help diagnose neurocysticercosis. Management generally includes anthelmintic therapy.
Meningitis is inflammation of the meninges, the protective membranes of the brain, and spinal cord. The causes of meningitis are varied, with the most common being bacterial or viral infection. The classic presentation of meningitis is a triad of fever, altered mental status, and nuchal rigidity. Diagnosis of meningitis is made on clinical grounds with a thorough neurologic examination. CSF analysis is an important diagnostic tool, as it is difficult to identify the exact cause clinically. Management of meningitis includes immediate broad-spectrum antibiotics and supportive therapy to prevent complications. Specific treatment depends on the etiology of meningitis. Delay in treatment can lead to permanent neurologic defects and death.
Equine encephalitis viruses (EEVs), belonging to the Togaviridae family and Alphavirus genus, are mosquito-borne arboviruses that infect humans and cause minor illness or, in severe cases, encephalitis. The eastern equine encephalitis (EEE) virus complex consists of the EEE virus, found in North America and the Caribbean; and the Madariaga virus, found in South and Central America. Other viruses in this complex include western EEV and Venezuelan EEV. The virus is maintained in a cycle between mosquitoes and avian hosts, but can spread to humans via bridge vectors (other species of mosquitoes). Initial symptoms after the mosquito bite include fever, headache, and vomiting. A majority of patients recover, but the illness can progress to severe encephalitis. Diagnosis is by clinical findings and CSF analysis using serology, and also by virus antigen or genomic sequence detection. There is no specific treatment, and therapy is largely supportive. Prevention of mosquito bites is key in management.
Hypernatremia is an elevated serum sodium concentration > 145 mmol/L. Serum sodium is the greatest contributor to plasma osmolality, which is very tightly controlled by the hypothalamus via the thirst mechanism and antidiuretic hormone (ADH) release. Hypernatremia occurs either from a lack of access to water or an excessive intake of sodium. The total volume of water lost (usually via GI or renal routes) is regained through normal oral intake. Therefore, if a patient has access to water and an intact thirst mechanism, many etiologies of hypernatremia may remain hidden. The etiology of hypernatremia is often easily determined by clinical history. Treatment is primarily a replacement of the free water deficit by IV or oral routes.
Malassezia is a lipophilic yeast commonly found on the skin surfaces of many animals, including humans. In the presence of certain environments or triggers, this fungus can cause pathologic diseases ranging from superficial skin conditions (tinea versicolor and dermatitis) to invasive disease (e.g., Malassezia folliculitis, catheter-associated fungemia, meningitis, and urinary tract infections). Patients with tinea versicolor develop an asymptomatic or mildly pruritic hypopigmented or hyperpigmented rash on the chest, back, abdomen, or face. Seborrheic dermatitis presents with an erythematous, pruritic rash with greasy scales and yellow crust, most commonly affecting areas of the face, upper trunk, or intertriginous regions. The presentation of Malassezia folliculitis is similar to that of bacterial folliculitis, with pruritic, monomorphic papules or pustules in a follicular pattern. The diagnosis of the superficial skin conditions is primarily by exam, but may be confirmed by microscopy of skin scrapings. Management entails the use of topical and oral antifungal agents.
Coxsackievirus is a member of a family of viruses called Picornaviridae and the genus Enterovirus. Coxsackieviruses are single-stranded, positive-sense RNA viruses, and are divided into coxsackie group A and B viruses. Both groups of viruses cause upper respiratory infections, rashes, aseptic meningitis, or encephalitis. Group A viruses cause herpangina; hand, foot, and mouth disease; and acute hemorrhagic conjunctivitis. Group B viruses cause myopericarditis, epidemic pleurodynia, and systemic neonatal disease. The diagnoses are usually made clinically. Viral culture and PCR can be performed for confirmation if the diagnosis is uncertain. Coxsackievirus infections are self-limiting and the management is supportive.
The gram-negative bacterium Escherichia coli is a key component of the human gut microbiota. Most strains of E. coli are avirulent, but occasionally they escape the GI tract, infecting the urinary tract and other sites. Less common strains of E. coli are able to cause disease within the GI tract, most commonly presenting as abdominal pain and diarrhea. E. coli is transmitted via a fecal–oral route, which can occur with unsanitary food preparation, contamination of meat or produce by manure, irrigating or washing crops/fruits with contaminated water, and consumption of contaminated water.
Essential thrombocythemia (ET) is a type of myeloproliferative neoplasm characterized by the clonal thrombocytosis linked to somatic mutations involving Janus kinase 2 (JAK2), calreticulin (CALR), and myeloproliferative leukemia virus oncogene (MPL). Patients can be asymptomatic or present with vasomotor symptoms such as headaches, erythromelalgia, and transient visual disturbances. The clinical course can be complicated by thrombohemorrhagic events as well as progression to myelofibrosis and AML. The diagnosis is based on a laboratory finding of thrombocytosis, bone marrow biopsy, and genetic studies. Treatment aims to reduce platelet count by cytoreductive agents (hydroxyurea) and to decrease thrombosis with aspirin and systemic anticoagulation based on thrombosis risk stratification.
Echoviruses are single-stranded positive-sense RNA viruses belonging to the genus Enterovirus. Transmission is most commonly through the fecal-oral route. The majority of patients are asymptomatic. Patients who are symptomatic can exhibit a wide range of illnesses ranging from nonspecific upper respiratory infections and exanthems to severe and life-threatening illnesses such as aseptic meningitis, encephalitis, and myocarditis. The diagnosis is usually made clinically, but laboratory confirmation using PCR and viral culture may be necessary for patients with severe disease. Most infections are self-limiting and require no specific therapy.
Herpes zoster (also known as shingles) is a viral, reactivation infection caused by the varicella-zoster virus (VZV). Latent VZV remains dormant in the dorsal root ganglion after the primary infection phase of varicella (chickenpox). Age, stress, or immunocompromised states can trigger the reactivation of the virus. Herpes zoster clinically presents in a single, dermatomal distribution as a painful, unilateral rash. The diagnosis is primarily made from the history and physical examination. However, laboratory testing (such as PCR) can be performed if the diagnosis is unclear. Management includes antiviral therapy and symptomatic treatment.
Restless legs syndrome (RLS), also known as Willis-Ekbom disease (WED), is marked by a severe urge to move the legs, and an unpleasant sensation only relieved by movement. Restless legs syndrome occurs after inactivity, especially during the evening and night, and is associated with sleep disturbance. The syndrome can be idiopathic, or due to secondary causes such as iron deficiency, pregnancy, diabetes mellitus, uremia, and Parkinson’s disease. Some drugs, most notably antidepressants and metoclopramide, can also trigger the syndrome. Management involves treatment of the underlying condition, supportive measures, and dopamine agonists.
Tick-borne encephalitis virus (TBEV) is a positive-sense, single-stranded RNA virus of the genus Flavivirus. Transmission occurs primarily via Ixodes ticks found in Europe, the former Soviet Union, and Asia. The virus causes tick-borne encephalitis. Most patients are asymptomatic; however, symptomatic individuals may experience a biphasic illness. After recovering from nonspecific symptoms, patients can develop neurologic manifestations, such as meningitis, encephalitis, or meningoencephalitis. Serology or PCR can confirm the diagnosis. There is no effective antiviral therapy for TBEV infections, so management is supportive.
The Saint Louis encephalitis virus (SLEV) is a member of the genus Flavivirus and is the cause of St. Louis encephalitis. This small, enveloped, positive-sense, single-stranded RNA virus is transmitted by Culex mosquito species and is prevalent in the United States. Most infections are asymptomatic. Symptomatic individuals may have varied presentations, with flu-like symptoms, aseptic meningitis, encephalitis, or meningoencephalitis. The diagnosis is confirmed with serology. There is no effective antiviral treatment, so management is supportive. Prevention is aimed at local mosquito control and personal protection with insect repellent and protective clothing.
Electrolytes are mineral salts that dissolve in water and dissociate into charged particles called ions, which can be either be positively (cations) or negatively (anions) charged. Electrolytes are distributed in the extracellular and intracellular compartments in different concentrations. Electrolytes are essential for various basic life-sustaining functions such as maintaining electrical neutrality in cells, generating action potentials in nerves and muscles, and maintaining normal blood pH. The most important electrolytes are sodium, potassium, chloride, magnesium, calcium, phosphate, and bicarbonate. In order for these electrolytes to participate in biochemical reactions and cellular processes, regulatory mechanisms are in place, which help maintain homeostasis.
Constipation is common and may be due to a variety of causes. Constipation is generally defined as bowel movement frequency < 3 times per week. Patients who are constipated often strain to pass hard stools. The condition is classified as primary (also known as idiopathic or functional constipation) or secondary, and as acute or chronic. Primary/functional constipation can be divided into normal transit, slow transit, and outlet constipation. Constipation is a symptom, not a disease, and appropriate management requires an evaluation of possible etiologies, such as systemic disorders and drugs. Once secondary causes have been eliminated, idiopathic constipation can be managed with lifestyle modifications and medications.
Minimal change disease (MCD), also known as lipoid nephrosis, is the most common cause of nephrotic syndrome in children. The designation “minimal change” comes from the very little changes noticed in kidney biopsies under light microscopy. Hallmark clinical findings include edema, proteinuria, hypoalbuminemia, and hyperlipidemia. Diagnosis is based on clinical suspicion and supportive lab findings. Corticosteroid administration is the cornerstone of management, and the prognosis is largely favorable.
Intestinal ischemia occurs when perfusion fails to meet the demands of the intestines, resulting in ischemic tissue injury that can be life-threatening if bowel necrosis and/or perforation occurs. Symptoms can range from mild indigestion or diarrhea to severe abdominal pain. Imaging techniques including CT and angiography are used to detect stenosis or occlusion. The chronic form of intestinal ischemia benefits from medical therapies and revascularization procedures (stents, bypass surgery) while acute forms require urgent interventions to restore blood flow and remove any dead bowel tissue. Delay in the diagnosis and management of acute intestinal ischemia results in high mortality and severe complications, including intestinal perforation and sepsis.
Pneumocystis jiroveci is a yeast-like fungus causing pneumocystis pneumonia (PCP) in immunocompromised patients. Pneumocystis pneumonia is spread through airborne transmission and classically affects patients with AIDS, functioning as an AIDS-defining illness. Patients may present with insidious onset of fever, chills, dry cough, chest pain, and shortness of breath. The diagnosis is supported by an increased β-D-glucan level and diffuse, bilateral infiltrates on chest imaging in the immunocompromised patient. A definitive diagnosis can be given with microscopy of induced sputum or specimens from bronchoalveolar lavage (BAL). Management involves antimicrobial therapy with a trimethoprim-sulfamethoxazole combination, and supportive care. Addressing the etiology of immunodeficiency is paramount. Prophylaxis is often required to prevent infection or reinfection.
Chronic eosinophilic leukemia (CEL) is a chronic myeloproliferative neoplasm caused by autonomous clonal proliferation of normal-appearing eosinophils, resulting in increased eosinophils in the peripheral blood and bone marrow. The disorder is a myeloid variant of hypereosinophilic syndrome (HES) and is associated with tissue infiltration leading to end-organ damage. Patients present with constitutional symptoms along with signs and symptoms of anemia and thrombocytopenia. Studies show absolute eosinophilic count ≥ 1.5 x 10⁹/L, with bone marrow blasts (5%–19%). Evidence of clonal abnormality or elevated blasts are needed; without either, idiopathic HES is the appropriate diagnosis. Nevertheless, both have a similar treatment approach. Management aims to reduce the burden of hypercellularity to prevent end-organ damage. Treatment options include corticosteroids, chemotherapeutic agents, and interferon-α.
Lymphatic filariasis, also known as elephantiasis, is a chronic mosquito-borne infection caused by Wuchereria bancrofti, Brugia malayi, and B. timori. The majority of causes are due to W. bancrofti. Mosquitos are the vectors, and humans are the primary reservoir. Patients with acute infection can present with fever, adenolymphangitis, dermatolymphangioadenitis, and tropical pulmonary eosinophilia. Patients with chronic infection present with lymphedema, which commonly affects the lower extremities (but can cause testicular swelling or hydrocele). Long-term effects also include renal manifestations. Thick and thin peripheral blood smears are the mainstay of diagnosis. Lymphatic filariasis without co-infection is generally managed with diethylcarbamazine. Prognosis is good with early diagnosis and intervention. Elephantiasis, or late-stage lymphedema, is associated with significant disability and would require different methods (including surgery) to reduce swelling and complications.
Hypercalcemia (serum calcium > 10.5 mg/dL) can result from various conditions, the majority of which are due to hyperparathyroidism and malignancy. Other causes include disorders leading to vitamin D elevation, granulomatous diseases, and the use of certain pharmacological agents. Calcium levels are regulated and affected by factors such as dietary intake and pH, and the levels of parathyroid hormone (PTH), vitamin D, and albumin. Symptoms vary depending on calcium levels and the onset of hypercalcemia. Generally, neuropsychiatric (confusion, altered mental status), GI (vomiting, abdominal pain), musculoskeletal (bone pain, weakness), and renal (polyuria, polydipsia) manifestations are seen. Confirmation of hypercalcemia is required. Correction of the value is based on the albumin levels or after determining the ionized calcium levels (the metabolically active form), which is followed by determining PTH levels. Subsequent laboratory tests and imaging studies are ordered based on history and presentation. Correction of hypercalcemia depends on its severity. Calcium levels > 14 mg/dL are treated using IV isotonic saline hydration, calcitonin, and bisphosphonates. Hemodialysis is considered in rare cases. Treatment of the underlying cause is recommended.
X-rays are high-energy particles of electromagnetic radiation used in the medical field for the generation of anatomical images. X-rays are projected through the body of a patient and onto a film, and this technique is called conventional or projectional radiography. As radiation by X-rays can cause adverse effects depending on the absorbed dose, it is necessary to take protective measures to reduce harm. Digital radiography uses the digital data format and allows for the digital manipulation of images. Common uses include evaluation of chest, mediastinal, spinal, and bone/joint conditions. While radiography is still used to visualize head and abdominal structures, more advanced modalities (CT and MRI) are now preferred. Radiography remains an essential component of initial tests in many diseases, given its wide availability, low cost, and ease of operation.
Statins are competitive inhibitors of HMG-CoA reductase in the liver. HMG-CoA reductase is the rate-limiting step in cholesterol synthesis. Inhibition results in lowered intrahepatocytic cholesterol formation, resulting in up-regulation of LDL receptors and, ultimately, lowering levels of serum LDL and triglycerides. Statins can lower LDL 20%–60% (depending on their intensity) and have benefits that are cholesterol-independent (e.g., reduced vascular inflammation and atherosclerotic plaque stabilization). Indications for prescribing statins include prevention of primary or secondary cardiovascular disease in patients with dyslipidemia. The main adverse effects are transaminitis and muscle toxicity.
Polycythemia vera (PV) is a chronic myeloproliferative neoplasm characterized by the overproduction of RBCs. In addition, the WBC and platelet counts are also increased, which differentiate PV from erythrocytosis seen with chronic hypoxia and other chronic conditions. Polycythemia vera is presumed to have a genetic basis due to mutations in the Janus kinase-2 gene. The clinical presentation includes disease-related symptoms that can affect various organ systems. Sometimes, the disease can be an incidental finding during laboratory testing. Diagnosis is based on peripheral blood analysis and bone marrow biopsy findings. Management is with phlebotomy or drug therapy. The prognosis is generally good and patient survival is anticipated to improve further with the wide use of new therapies.
Astrocytomas are neuroepithelial tumors that arise from astrocytes, which are star-shaped glial cells (supporting tissues of the CNS). Astrocytomas are a type of glioma. There are 4 grades of astrocytomas. Grade I tumors are typically benign and present in children, while grade IV tumors (known as glioblastoma multiforme) are the most common primary malignant brain tumor in adults and have a particularly poor prognosis. The etiology of astrocytomas is usually unknown. The exact presenting symptoms depend on the tumor location and grade, but patients may exhibit headaches, seizures, and/or focal neurologic deficits. Diagnosis is made by MRI and tissue biopsy. Treatment depends on the grade of the tumor and may include any combination of surgery, radiation therapy, and/or chemotherapy.
The vertebral column is the most important anatomical and functional axis of the body, consisting of 7 cervical, 12 thoracic, and 5 lumbar vertebrae and limited cranially by the skull and caudally by the sacrum. The vertebral column provides structural support and protection for the spinal cord, which is housed in the spinal canal. The vertebral column and the spinal cord may be affected by various diseases, in which different imaging methods are important for correct diagnosis and management. Radiographs and CT scans are useful in evaluating bony structures, especially in excluding fractures and checking hardware. Additionally, CT scans also provide information on soft tissues. MRI is performed for evaluation of tumors, infection, disk herniations, and other soft tissue abnormalities including acute ligamentous or spinal cord injury.
Chronic kidney disease (CKD) is kidney impairment that lasts for ≥ 3 months, implying that it is irreversible. Hypertension and diabetes are the most common causes; however, there are a multitude of other etiologies. In the early to moderate stages, CKD is usually asymptomatic and is primarily diagnosed by laboratory abnormalities. Regardless of the etiology, progression of renal impairment is common and can ultimately lead to end-stage renal disease and the need for renal replacement therapy (e.g., transplantation or dialysis). The management of CKD includes treating the underlying etiology, aggressive risk factor modification, and addressing complications such as fluid overload and electrolyte imbalances.
Sleep is a reversible phase of diminished responsiveness, motor activity, and metabolism. This process is a complex and dynamic phenomenon, occurring in 4–5 cycles a night, and generally divided into non–rapid eye movement (NREM) sleep and REM sleep stages. NREM sleep, consisting of 3 stages, represents the period of transition from wakefulness, somnolence, and then deep sleep. REM sleep is characterized by rapid irregular eye movement, but with voluntary muscle atonia. The sleep stages and associated disorders are studied through the use of polysomnography, a multimodal test evaluating the brain waves, along with ocular and motor activities. Sleep disorders can be primary (which do not stem from any health problem) or can be attributable to underlying conditions or medications.
Circadian rhythm sleep–wake disorders are a group of conditions marked by recurrent patterns of sleep disruption. These disorders can be due to an alteration of the circadian system (intrinsic) or a misalignment between an individual’s inner circadian rhythm and the environment (extrinsic). The disruption impairs the individual’s daily activities. There are 6 different subtypes, including delayed and advanced sleep–wake phase disorder, irregular and non-24-hour sleep–wake rhythm disorder, shift-work disorder, and jet lag. Diagnosis is generally clinical, but using tools such a sleep diary and actigraphy help in determining the disorder. Management for circadian rhythm sleep–wake disorders involves light therapy, behavioral modification, and pharmacotherapy, such as with melatonin.
Tics and related diseases represent a set of neurobehavioral disorders of childhood that are characterized by sudden, repeated, nonrhythmic, stereotyped muscle movements sometimes accompanied by sounds or vocalizations. Tourette syndrome is a severe form with symptoms lasting more than 1 year and involving both motor and vocal tics. Although there is no definitive cause of Tourette syndrome, the condition has genetic and environmental factors that contribute to disease development. Tourette syndrome is clinically diagnosed. Treatment involves behavioral therapy, antipsychotics, and the treatment of comorbid conditions. The majority of children outgrow their symptoms in adulthood, although a minority of adults will continue to demonstrate severe tics.
Varicella-zoster virus (VZV) is a linear, double-stranded DNA virus in the Herpesviridae family. Varicella-zoster infections are highly contagious and transmitted through aerosolized respiratory droplets or contact with infected skin lesions. Chickenpox is the primary infection and occurs most commonly in children. The typical clinical presentation includes prodromal symptoms and a generalized, intensely pruritic vesicular rash. Shingles (also known as herpes zoster) is more common in adults and occurs due to the reactivation of VZV. The diagnosis is primarily clinical. Management is supportive, although antiviral therapy can be used in certain patient populations. Complications can include secondary bacterial infections, encephalitis, or pneumonia. Varicella-zoster vaccine is recommended as a preventive measure in early childhood.
Coronaviruses are a group of related viruses that contain positive-sense, single-stranded RNA. Coronavirus derives its name from "κορώνα" in Greek, which translates as “crown,” after the small club-shaped proteins visible as a ring around the viral envelope in electron micrographs. Coronaviruses have large genomes, a propensity for mutation, and frequent recombination events that have resulted in a diversity of species. These new species are capable of rapid adaptation to new hosts and ecologic environments. New coronavirus infections have appeared in both humans and animals. Coronaviruses are known to be the cause of some cases of the common cold, severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and coronavirus disease 2019 (COVID-19).
Medulloblastomas are malignant primitive neuroectodermal tumors that arise in the posterior fossa in children. Medulloblastomas are the most common malignant brain tumors in children. Patients with medulloblastoma present with symptoms of increased intracranial pressure and cerebellar signs, which both evolve and worsen over weeks to a few months. Magnetic resonance imaging is the imaging modality of choice and typically shows a midline or paramedian cerebellar mass that enhances with contrast, but histopathological analysis after surgical resection is required for diagnosis. Treatment involves a combination of surgery, radiation therapy, and chemotherapy. Prognosis depends on a variety of factors, but with modern multimodality therapy, roughly 75% of children diagnosed with medulloblastoma survive into adulthood.
Glioblastoma multiforme is a high-grade astrocytoma, an aggressive brain tumor arising from astrocytes, with an unknown cause and a poorly understood link to risk factors. There are two main types: primary, a more aggressive form seen more commonly in older patients, and secondary, developing from lower-grade astrocytomas and seen more commonly in younger patients. Glioblastomas most commonly present with headache, seizures, and neurologic deficits. MRI is the gold standard diagnostic tool, and surgical resection combined with radiation and chemotherapy is the treatment of choice. Prognosis is extremely poor, with survival of only 1–5 years in patients receiving aggressive treatment and only 3 months in patients who do not undergo treatment.
Meningiomas are slow-growing tumors that arise from the meninges of the brain and spinal cord. The vast majority are benign. These tumors commonly occur in individuals with a history of high doses of skull radiation, head trauma, and neurofibromatosis 2. Clinical symptoms of meningioma depend on the location and progression of the tumor, with a large proportion of meningiomas being asymptomatic. When symptoms do develop, they most commonly include headache, seizures, visual disturbances, and other focal neurologic deficits. Diagnosis is made based on neuroimaging (MRI is the gold standard) and biopsy. Management involves surveillance for asymptomatic patients and, for symptomatic patients, surgical resection. Radiation is also used in some cases.
Schwannomas (also known as neurilemmomas) are benign nerve sheath tumors in the peripheral nervous system (PNS), arising from Schwann cells that encase the peripheral nerves. Schwannomas are the most common tumors in the PNS. Although schwannomas are typically sporadic, they can be associated with neurofibromatosis type II and schwannomatosis. The clinical presentation of schwannomas depends on their specific location, but general signs and symptoms include a palpable mass on the skin, pain, and/or paresthesias due to nerve compression. The diagnosis is established primarily based on imaging studies (MRI or CT), and the treatment is usually surgical resection.
Acoustic neuroma, also referred to as vestibular schwannoma, is a benign tumor arising from Schwann cells of the vestibular component of the cranial nerve VIII. Acoustic neuroma forms within the internal auditory meatus and extends into the cerebellopontine angle. Vestibular schwannoma is mostly unilateral. Bilateral vestibular schwannomas are associated with neurofibromatosis type II. Symptoms arise due to compression of the cranial nerves V, VII, and VIII, and the cerebellum. The most common complaint is unilateral hearing loss but acoustic neuroma can also present with vertigo, decreased facial sensation, Bell’s palsy, and ataxia. Diagnosis of vestibular schwannoma is made with MRI of the brain with contrast. Treatment depends on the size of the tumor and symptom severity. Large tumors with severe hearing loss are treated with surgical excision or radiation therapy, while small tumors with mild symptoms can be observed over time.
Post-streptococcal glomerulonephritis (PSGN) is a type of nephritis that is caused by a prior infection with group A beta-hemolytic Streptococcus (GAS). The clinical presentation of PSGN can range from asymptomatic, microscopic hematuria to full-blown acute nephritic syndrome, which is characterized by red-to-brown urine, proteinuria, edema, and acute kidney injury. The diagnosis is made based on clinical findings in the setting of recent GAS infection. Management is supportive and involves treating the clinical manifestations. The prognosis is generally favorable, especially in children.
Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of
Chronic lymphocytic leukemia (CLL) is a hematologic malignancy characterized by excess production of monoclonal B lymphocytes in the peripheral blood. When the involvement is primarily nodal, the condition is called small lymphocytic lymphoma (SLL). The disease usually presents in older adults, with a median age of 70 years. Clinical presentation is often asymptomatic and diagnosis is made when abnormal lymphocytosis is seen on laboratory testing. Cytopenias can also be seen. The B cells are functionally incompetent lymphocytes and thus may result in recurrent infections. Treatment can vary from watchful waiting for early stages to chemotherapy for later stages. Median survival is around 10 years.
Oligodendrogliomas are malignant CNS tumors arising from neural glial cell precursors. Oligodendrogliomas often arise in the frontal lobes of the brain and have a generally favorable prognosis when compared to other gliomas. Oligodendrogliomas are the 3rd most common CNS tumor. The most frequent presenting symptom is a seizure; other symptoms include headaches, visual loss, and focal neurologic deficits. Diagnosis is established by brain biopsy that demonstrates a classic “fried egg” appearance (round nuclei with clear cytoplasm). Oligodendrogliomas are slow-growing, but because they are life-limiting, they are managed with a combination of surgical resection, radiation, and chemotherapy.
A fracture is a disruption of the cortex of any bone and periosteum and is commonly due to mechanical stress after an injury or accident. Open fractures due to trauma can be a medical emergency. Fractures are frequently associated with automobile accidents, workplace injuries, and trauma. Clinical presentation varies depending on the cause and location of the injury, but generally includes deformity, pain, edema, and inflammation. Diagnosis is made clinically and confirmed with imaging, and management may be with splinting or may require surgery.
Imaging of the brain is most commonly used for evaluating trauma, stroke, and benign or malignant tumors. Before the advent of CT and MRI, X-ray scanning was widely used to study the skull and spinal bones. Today, CT and MRI, especially the latter, are the preferred imaging methods for the study of the cranial vault and its contents. In conditions where emergent management is decided on the basis of presentation and imaging, CT has the advantage of rapid scan time and wider availability. CT also has good sensitivity and specificity and relatively lower cost. MRI though, provides better parenchymal characterization especially in cases where initial findings are negative on CT (such as in acute ischemia).
Hemangioblastomas are vascular neoplasms of the CNS. Hemangioblastomas are rare and are often associated with von Hippel-Lindau disease (VHL). The most common presentation is a headache and, depending on the size and location of the tumor, patients may present with sensory deficits and motor weakness. Imaging is the main screening method, with histopathologic evaluation required for definitive diagnosis. Surgery is often indicated in the management of hemangioblastomas, though depending on the size, number, and location of the tumors, radiation therapy may also be warranted. Prognosis is usually good in solitary hemangioblastomas, but tumors associated with VHL are often associated with a worse prognosis and a higher risk of recurrence.
Human papillomavirus (HPV) is a nonenveloped, circular, double-stranded DNA virus belonging to the Papillomaviridae family. Humans are the only reservoir, and transmission occurs through close skin-to-skin or sexual contact. Human papillomaviruses infect basal epithelial cells and can affect cell-regulatory proteins to result in cell proliferation. There are > 200 serotypes that can cause several conditions, including cutaneous warts, anogenital warts, and neoplasms.
Mucormycosis is an angioinvasive fungal infection caused by multiple fungi within the order, Mucorales. The fungi are ubiquitous in the environment, but mucormycosis is very rare and almost always occurs in patients who are immunocompromised. Inhalation of fungal spores can cause rhinocerebral or pulmonary mucormycosis, direct inoculation can cause cutaneous mucormycosis, and ingestion can cause gastrointestinal mucormycosis. The clinical presentation results from fungal hyphae invading the blood vessels, causing thrombosis and tissue necrosis. Diagnosis is confirmed with the identification of the organism on histopathology of biopsy specimens. Patients must be treated aggressively with antifungals and surgical resection of infected tissues.
Craniopharyngiomas are rare squamous epithelial tumors with a solid and/or cystic structure that arise from the remnants of Rathke’s pouch along the pituitary stalk, in the suprasellar region. Craniopharyngiomas are histologically benign but tend to invade surrounding structures; thus, they should be treated as low-grade malignancies. Histologically, there are 2 types of tumors: adamantinomatous, which is more common in children; and papillary, which tends to occur in adults. Both these types can present with various symptoms depending on their location and extension patterns. The symptoms include headaches, nausea, vomiting, visual disturbances, endocrine dysfunction, and behavioral issues. Diagnosis is made by imaging and histology. Management typically involves surgical excision and radiation therapy.
Neuroblastoma is a malignancy that arises from the neural crest cell derivatives along the sympathetic chain (neuroblasts) and is most commonly located in the adrenal medulla. The tumor often presents in childhood with a flank mass that crosses the midline. Neuroblastoma can also manifest as opsoclonus-myoclonus paraneoplastic syndrome. The tumor is diagnosed through biopsy, and supporting data include measuring the catecholamine breakdown products such as vanilmandelic acid (VMA) and homovanillic acid (HVA) in urine. Imaging studies are needed to localize the tumor. Management depends on several factors such as the stage of malignancy and the patient’s age at the time of diagnosis. Prognosis is favorable in the early stages of neuroblastoma.
Acromegaly and gigantism are caused by an excessive production of growth hormone (GH) by the pituitary gland. Tall stature is a clinical sign observed in some patients with gigantism. Increased GH and insulin-like growth factor-1 (IGF-1) are responsible for inducing hypersomatotropism. Acromegaly is usually produced by pituitary tumors secreting GH or, less commonly, by extrapituitary disorders. Gigantism typically results in children from excess GH before growth-plate closure; acromegaly typically results from excess GH after growth-plate closure. Diagnosis involves neuroimaging of the pituitary and laboratory tests to evaluate the hypothalamic-pituitary axis. Treatment depends on the operative status of the tumor (if present), or a nonoperative treatment strategy may be utilized.
An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Electrocardiograms are simple, inexpensive, noninvasive, and readily obtained. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. In the healthy state, an ECG records predictable, reproducible waves and complexes, which correspond to electromechanically coupled physiologic events in the heart. Under pathologic conditions, the ECG can detect arrhythmias, ischemia, inflammation, and more.
Parasomnias are a pattern of sleep disorders marked by unusual actions, activities, or physiological events that occur during sleep or sleep-wake transitions. Parasomnias are divided into which sleep phase the symptoms occur, either rapid eye movement (REM) or non-REM (NREM). Symptoms may include simple or complex abnormal movements, such as sleep talking, sleepwalking, sleep terrors, and dream enactment, or emotions, dreams, and autonomic activity. Diagnosis involves a thorough history taking from the patient and the partner. In some cases, polysomnography is required, especially if comorbid sleep disorders are suspected. Some conditions resolve over time without any treatment. For those that require intervention, options include lifestyle or risk modifications, different forms of therapy, and medications. Choice of management is affected by patient preferences.
Insomnia is a sleep disorder characterized by difficulty in the initiation, maintenance, and consolidation of sleep, leading to impairment of function. Patients may exhibit symptoms such as difficulty falling asleep, disrupted sleep, trouble going back to sleep, early awakenings, and feeling tired upon waking. The disorder can be acute (< 3 months), which can progress to the chronic form (≥ 3 months). Multiple risk factors contribute to having insomnia, including medical illnesses, psychiatric disorders, medications, and the sleep environment. Diagnosis starts with a detailed history and sleep diagnostic aids (sleep diary, sleep problems questionnaire). The 1st line of management is nonpharmacologic, i.e., identifying the stressor(s), implementing sleep hygiene, and utilizing cognitive behavioral therapy. Medications are used with nonpharmacologic intervention or after initial management has failed.
An infection is the proliferation of microorganisms within tissues, body cavities, or spaces, which induces an immune response and overwhelms the body’s natural defenses. In surgical patients, these infections are frequently caused by the translocation of commensal organisms into deeper tissues, combined with the impairment of host defenses due to surgical injury or stress. Infections commonly identified in patients after surgery include surgical site infections, catheter-associated infections, and ventilator-associated infections. Infection subtypes can be prevented, diagnosed, or treated using several strategies. The mainstays of treatment in surgical patients involve local control of the infection as well as targeted antibiotic therapy.
Stable and unstable angina are considered an important symptom of coronary heart disease (CHD) and present with chest pain due to transient myocardial ischemia. These disorders can be a warning sign for the risk of heart attack (MI) in the future. Clinically, stable and unstable angina are differentiated by exacerbating factors, duration of symptoms, and response to rest and medications. Diagnosis is by history and examination, ECG, stress testing with possible additional nuclear medicine imaging, echocardiography, or coronary angiography. Management with lifestyle modifications and aggressive risk factor reduction (of hypertension, diabetes, and hyperlipidemia) is indicated to prevent the risk of progression to MI and death.
MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Diagnosis is by clinical history, ECG changes, an increase in cardiac enzymes, and evidence of wall motion abnormalities on imaging. Management depends on the timing of the presentation and local resources with regard to thrombolytic therapy versus percutaneous intervention. All patients receive nitrates, pain control, aspirin, anticoagulation, and beta-blockers (unless contraindicated).
Testicular cancer is the most common solid malignancy affecting men 15–35 years of age. Most of the testicular cancers are of the germ cell tumor type, and they can be classified as seminomas and nonseminomas. The most common presentation of testicular cancer is a painless testicular mass. Diagnosis is via physical exam, testicular ultrasonography, and serum tumor markers. Additional imaging helps with staging and assessment of metastasis. Treatment consists of surgical inguinal orchiectomy, and further adjuvant therapy is based on disease pathology and stage. Subsequent strategies include disease surveillance, radiotherapy, and chemotherapy. Disease prognosis is excellent, as testicular cancer is one of the most curable solid neoplasms.
Acute myeloid leukemia (AML) is a hematologic malignancy characterized by the uncontrolled proliferation of myeloid precursor cells. Seen predominantly in older adults, AML includes an accumulation of myeloblasts and a replacement of normal marrow by malignant cells, which leads to impaired hematopoiesis. Clinical presentation consisting of fatigue, bleeding, fever, and infection is related to anemia, thrombocytopenia, and a lack of functional WBCs. The onset of symptoms takes days to weeks. Additional findings in AML may include gingival hypertrophy and skin infiltration (leukemia cutis). Diagnosis is via peripheral blood smear and bone-marrow biopsy examination (shows myeloblasts). The precursor cells contain Auer rods. Immunophenotyping, histochemistry, and genetic analysis all aid in identifying and guiding the treatment of AML. Management is chemotherapy administered in phases (induction, consolidation, and maintenance) based on subtypes. Prognosis varies according to the age of onset and type of leukemia.
Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia is most commonly seen in diabetic patients as a result of inadequate oral intake with insulin administration, but it can also be seen in hypermetabolic states, such as sepsis, or malnutrition states, such as chronic alcohol use or prolonged fasting. Hyopoglycemia may present with a variety of nonspecific symptoms, including adrenergic symptoms (sweating, tachycardia, tremulousness) and neuroglycopenic symptoms (dizziness, confusion, lethargy, loss of consciousness). Diagnosis is based on serum glucose measurement and clinical presentation. Management depends on the severity of symptoms. A patient with normal mental status may be able to take oral glucose gel or sugary drinks, but a patient with altered mental status will need IV dextrose and frequent serum glucose checks.
Mitochondrial myopathies are conditions arising from dysfunction of the mitochondria (the energy-producing structures) and are characterized by prominent muscular symptoms and accompanied by various symptoms from organs with high energy requirements. The organs disproportionately affected include the skeletal muscles, brain, and heart. Mitochondrial myopathies are caused by mutations in the nuclear DNA or mitochondrial DNA, which typically result in reduced production of energy needed by cells. Presentation can be an isolated myopathy, encephalomyopathy, ophthalmoplegias, or a multisystem disease. Diagnosis involves in-depth medical and family history, along with laboratory and genetic studies. On biopsy, there is subsarcolemmal and intermyofibrillar proliferation of mitochondria seen as “ragged-red fibers.” This condition indicates a compensatory response to energy failure. There is no definitive treatment. Management consists of physical therapy and a multidisciplinary approach in addressing accompanying symptoms.
Herpes simplex virus (HSV) is a double-stranded DNA virus belonging to the family Herpesviridae. Herpes simplex virus commonly causes recurrent infections involving the skin and mucosal surfaces, including the mouth, lips, eyes, and genitals. Typical mucocutaneous infections are characterized by an acute localized appearance of clusters of small, painful vesicles on an erythematous base. Although overlap exists, HSV-1 is classically associated with oropharyngeal lesions, whereas HSV-2 is mostly responsible for genital herpes, an STI. Systemic and severe infections including encephalitis, meningitis, and neonatal herpes may also occur. The diagnosis is made based on clinical presentation and history, which can be confirmed by the microscopic examination of a stained smear of a fresh vesicle, nucleic amplification test using PCR, direct immunofluorescence, or serologic tests. The therapy for mucocutaneous lesions is usually symptomatic, but antiviral therapies involving acyclovir, valacyclovir, or famciclovir are useful if given early, and are always part of the therapy for serious systemic infections.
Cryptococcosis is an opportunistic, fungal infection caused by the Cryptococcus species. The principal pathogens in humans are C. neoformans (primary) and C. gattii. Cryptococcus neoformans is typically found in pigeon droppings and acquired by inhaling dust from contaminated soil. The majority of affected patients are immunocompromised. Patients with AIDS, chronic steroid use, and organ transplant are particularly affected. The primary virulence factor is an antiphagocytic capsule, consisting of repeating capsular polysaccharide antigens. The infection typically affects the lungs and presents as a primary lesion or pneumonia. Dissemination can occur to involve the brain and meninges, skin, bones, and visceral organs. Treatment for cryptococcal meningitis is usually amphotericin B and flucytosine, followed by fluconazole. Cryptococcosis is an AIDS-defining illness and typically associated with CD4 count < 100 cells/μL.
Acute lymphoblastic leukemia/lymphoma (ALL/LBL) are hematologic malignancies characterized by the uncontrolled proliferation of lymphoid precursor cells. Acute lymphoblastic leukemia/lymphoma, the most common forms of cancer affecting children, show the presence of increased lymphoblasts. In ALL/LBL, lymphoblasts replace the normal marrow, eventually entering the circulation and infiltrating other organs. The clinical presentation includes fatigue, bleeding, fever, and infections, all of which are related to anemia, thrombocytopenia, and the lack of functional WBCs. The onset of symptoms takes days to weeks. Mass effects of malignant infiltration (in bone, liver, spleen) are common; thus, hepatosplenomegaly and lymphadenopathy are seen. Diagnosis is by peripheral blood smear examination and bone marrow biopsy, which show the presence of lymphoblasts. Immunophenotyping, histochemistry, and genetic studies aid in the classification and guidance of treatment. Management is mainly by chemotherapy, which is administered in phases (induction, consolidation, and maintenance). Prognosis varies according to the age of onset and type of leukemia. The cure rate in children is 85%.
Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. The disorder can usually be managed with lifestyle modification and medications, but occasionally, vascular intervention or surgery are required. Age, sex, smoking, obesity, and diet are contributing factors to hypertension, which can lead to heart attack, stroke, congestive heart failure, and CKD if not managed properly. Many individuals with hypertension are undiagnosed or undertreated.
Thiazide and thiazide-like diuretics make up a group of highly important antihypertensive agents, with some drugs being 1st-line agents. The class includes hydrochlorothiazide, chlorothiazide, chlorthalidone, indapamide, and metolazone. These drugs block sodium reabsorption in the distal convoluted tubule of the kidney by inhibiting the sodium-chloride cotransporter. As a result, the increased sodium excretion causes secondary water excretion because water follows the sodium. In addition to increasing sodium and water excretion, thiazide diuretics also cause the excretion of chloride, potassium, magnesium, and protons (H+).
Hypogonadism is a condition characterized by reduced or no sex hormone production by the testes or ovaries. Hypogonadism can result from primary (hypergonadotropic) or secondary (hypogonadotropic) failure. Hypergonadotropic hypogonadism results when the gonads fail, and hypogonadotropic hypogonadism results from failures in the hypothalamic–pituitary–gonadal axis. Symptoms include infertility, increased risk of osteoporosis, erectile dysfunction, decreased libido, and regression (or absence) of secondary sexual characteristics. Diagnosis is guided by the history, physical exam, measurement of hormone levels, and an evaluation for an underlying etiology. Management is with hormone replacement.
A toxidrome is a group of clinical signs and symptoms associated with a toxic ingestion or exposure. There are 5 traditional toxidromes: anticholinergic, cholinergic, opioid, sympathomimetic, and sedative-hypnotic. Toxidromes often arise from ingestion of overdose amounts, accumulation of medications with resultant elevated serum levels, adverse drug reactions, or interactions between 2 or more medications. Rapid recognition of a toxidrome can help determine the specific poison or class of toxin that was ingested. On presentation of a suspected toxidrome, appropriate airway, breathing, and circulation assessment is initiated. Decontamination is performed, and the patient is stabilized. Diagnosis is accomplished with clinical findings based on medication and exposure history, vital signs, mental status, and physical examination. Testing generally includes toxicology and drug levels, electrolytes, and ECG. Management consists of supportive care and antidote administration if indicated.
Internuclear ophthalmoplegia (INO) is an ocular movement disorder that affects the conjugate horizontal gaze, meaning the eyes are incapable of moving in a simultaneous and coordinated manner on the horizontal plane. This disorder is usually caused by a lesion in the brain stem involving the medial longitudinal fasciculus (MLF) and is characterized by impaired adduction ipsilateral to the MLF lesion and abduction nystagmus contralateral to the MLF lesion. Internuclear ophthalmoplegia is a clinical diagnosis. However, investigations involving neuroimaging, especially MRI, help establish the diagnosis. Management of INO varies depending on the cause. The prognosis mainly depends on the etiology. For instance, trauma patients do not have a very favorable prognosis, whereas patients with ischemic and demyelinating causes have a favorable recovery.
Disease-modifying antirheumatic drugs are antiinflammatory medications used to manage rheumatoid arthritis. The medications slow, but do not cure, the progression of the disease. The medications are classified as either synthetic or biologic agents and each has unique mechanisms of action and side effects. Common side effects among the disease-modifying antirheumatic drugs include bone marrow suppression and hepatotoxicity. Leflunomide, methotrexate, and tumor necrosis factor (TNF)-ɑ inhibitors are avoided in pregnancy due to their potential teratogenicity. Hydroxychloroquine and sulfasalazine are safe for use during pregnancy.
Myotonic dystrophies are genetic disorders due to autosomal-dominant genetic mutations and have 2 major clinical forms: myotonic dystrophy type 1 (DM1) and myotonic dystrophy type 2 (DM2). Myotonic dystrophies are heterogeneous diseases primarily affecting the muscles, but, unlike other muscular dystrophies, also have multisystem effects. Both DM1 and DM2 present with myotonia, muscle weakness, and myalgias; however, DM1 is severe and carries a reduced life expectancy, whereas DM2 is mild with a normal life expectancy. Diagnosis is made clinically, with genetic testing, and by electromyography (EMG). Management is primarily supportive.
Porphyrias are a group of metabolic disorders caused by a disturbance in the synthesis of heme. In most cases, porphyria is caused by a hereditary enzyme defect. The disease patterns differ depending on the affected enzyme, and the variants of porphyria can be clinically differentiated between acute and nonacute forms. Patients with porphyria present with photosensitive skin eruptions and sometimes systemic symptoms such as abdominal pain and neuropathy. Porphyrias are managed by avoiding triggers, such as sun exposure and consumption of alcohol. When flares occur, therapy is targeted toward symptomatic relief.
Herbicides are chemical substances used to kill or control the growth of unwanted plants. Important herbicides that can affect humans include paraquat, Agent Orange, glyphosate, and organophosphates. Different types of herbicides result in different clinical manifestations and have various toxicity levels. Paraquat ingestion is associated with multiorgan damage within a few hours and is fatal in large amounts. In contrast, glyphosate typically has low toxicity, but if a significant volume is ingested, serious adverse effects occur. Organophosphates, which are broadly used as pesticides, produce a cholinergic toxidrome. Agent Orange, containing 2,3,7,8-tetrachlorodibenzo-p-dioxin, a human carcinogen, carries both short-term (e.g., chloracne, liver toxicity) and long-term (e.g., cancers) complications. Exposure can be dermal or via inhalation or ingestion. In general, early detection is important to prevent serious sequelae. Initial management consists of stabilizing the patient and decontamination. An antidote is given, if available. Treatment of herbicide poisoning revolves around supportive care that depends on the involved organ system.
Acute limb ischemia (ALI) is a major vascular emergency because of the rapid decrease in limb perfusion that causes a potential threat to limb viability. The majority of cases are caused by arterial thrombosis due to plaque progression or embolism, but ALI can also be caused by blockage of the venous drainage. The typical signs and symptoms of ALI are often referred to as the 6 Ps: pain, pallor, poikilothermia, paralysis, paresthesia, and pulselessness. The diagnosis is made on the basis of clinical findings and Doppler studies, but additional imaging may be required. Management is focused on revascularization. IV heparin is also administered. Nonviable limbs require amputation.
Hidradenitis suppurativa (HS) is a chronic skin condition due to the inflammation of apocrine sweat glands and hair follicles. Most commonly, it occurs due to occlusion of the follicular component of pilosebaceous units (PSUs). The condition is characterized by the formation of abscesses, fistulas, draining skin lesions, keloids, and pilonidal sinuses. The diagnosis of HS is primarily clinical. Management includes lifestyle counseling regarding weight loss and smoking cessation, as well as medical treatment with antibiotics and retinoids. Untreated HS can result in fibrosis with scarring of the skin as a complication.
Von Willebrand disease (vWD) is a bleeding disorder characterized by a qualitative or quantitative deficiency of von Willebrand factor (vWF). Most cases are hereditary, but acquired forms have been described. Von Willebrand factor is a multimeric protein involved in the plate adhesion phase of hemostasis by forming a bridge between platelets and damaged portions of the vessel wall. Von Willebrand factor also regulates the levels of coagulation factor VIII (FVIII) by acting as its carrier. Clinical features vary depending on the plasma vWF levels. Most cases are asymptomatic, but patients may present with petechiae, gingival bleeding, epistaxis, or menorrhagia. The diagnosis primarily depends on the clinical history and laboratory assays, including quantitative measurement of vWF, vWF ristocetin cofactor activity (vWF:RCo) assay, and FVIII coagulant assay. Management is based on the subtype of the disease. The most common agents used are desmopressin acetate and concentrates containing recombinant vWF and FVIII.
Although hepatocellular carcinoma (HCC) is by far the most common malignant liver tumor, there are several rare malignant tumors that are important to keep in mind when making a differential diagnosis. These tumors include cholangiocarcinoma; hepatoblastoma and mesenchymal tumors, such as epithelioid hemangioendothelioma (EHE); and angiosarcoma. While these conditions differ in their etiology and pathology, they often present similarly, with nonspecific symptoms such as fatigue, weight loss, and abdominal discomfort. Diagnosis is by imaging, which can be supported by a biopsy. Surgical excision is the only curative approach for these tumors.
An antidote is a substance that counteracts poisoning or toxicity. Substances that can cause poisoning include heavy metals (from occupation, treatments, or diet), alcohols, environmental toxins, and medications. An increase in the concentration of these substances to toxic levels can occur accidentally or intentionally, resulting in both acute and chronic presentations. Some substances can be detected using specific laboratory tests, whereas the detection of others relies on nonspecific findings. Thus, it is important to recognize substance poisoning by history, individual risk factors, and physical examination. Antidotes along with supportive care and monitoring are part of the management.
Insecticides are chemical substances used to kill or control insects, to improve crop yields, and to prevent diseases. Human exposures to insecticides can be by direct contact, inhalation, or ingestion. Important insecticides that can affect humans include organochlorines (dichlorodiphenyltrichloroethane (DDT)), organophosphates (malathion and parathion), and carbamates (carbaryl, propoxur, aldicarb, and methomyl). Because of DDT's long-term adverse effects on wildlife and the environment, it is now not used in many areas. However, it is still in use in areas with high rates of malaria infection. The chemical produces neurotoxicity and endocrine disruption. Organophosphates and carbamates produce cholinergic effects, given their similar mechanism of action of inhibiting acetylcholinesterase. Organophosphates, though, bind the enzyme irreversibly, while carbamates inhibit the enzyme for < 48 hours. Diagnosis is based on history and clinical findings, with tests available for confirmation. Management involves decontamination, supportive care, and symptom control. For the cholinergic toxidrome, atropine and pralidoxime are given to reverse the effects of cholinergic excess.
Autism spectrum disorder (ASD) is a neurodevelopmental disorder marked by poor social skills, restricted interests/social interactions, and repetitive/stereotyped behaviors. The condition is termed a “spectrum” because of the wide variability in the severity of symptoms exhibited. Some patients suffer from severe impairment in language and intellectual levels, while others have normal or even advanced intellect. The etiology is not well understood and there is no known cure. Early diagnosis and intervention are important in improving the patient’s symptoms.
Generalized anxiety disorder (GAD) is a common mental condition defined by excessive, uncontrollable worrying causing distress and occurring frequently for at least 6 months. Generalized anxiety disorder is more common in women. Among the risk factors are family history, other mental health disorders, chronic physical illness, and a history of abuse or trauma. Clinical presentation includes fatigue, low concentration, restlessness, irritability, and sleep disturbance. Diagnosis is clinical but if history suggests an underlying disease, laboratory tests are obtained. Treatment includes a combination of psychotherapy (e.g., CBT) and medications such as selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs).
Human herpesvirus 8, also known as Kaposi sarcoma–associated herpesvirus, is a double-stranded DNA virus belonging to the Herpesviridae family. This uncommon oncogenic virus causes Kaposi sarcoma (an AIDS-defining condition), primary effusion lymphomas, and multicentric Castleman disease mainly in immunocompromised patients. The process occurs through the induction of cellular growth activity and the inhibition of apoptosis in infected cells.
Hepatocellular carcinoma (HCC) typically arises in a chronically diseased or cirrhotic liver and is the most common primary liver cancer. Diagnosis may include ultrasound, CT, MRI, biopsy (if inconclusive imaging), and/or biomarkers. Treatment options include resection and chemo-/radiotherapy, and liver transplantation in select cases. Liver metastases are much more common than primary liver cancers and usually originate from colorectal, lung, breast, and pancreatic primary sites. Metastases are most commonly diagnosed by CT or PET scans. Management depends on the type and stage of primary cancer.
Triptans and ergot alkaloids are agents used mainly for the management of acute migraines. The therapeutic effect is induced by binding to serotonin receptors, which causes reduced vasoactive neuropeptide release, pain conduction, and intracranial vasoconstriction. Triptans are the preferred therapy, followed by ergot alkaloids, but both agents have good efficacy. Due to the vasoconstriction effect, the medications should not be used concurrently or be prescribed to patients with cardiovascular disease.
Endometritis is an inflammation of the endometrium, the inner layer of the uterus. The most common subtype is postpartum endometritis, resulting from the ascension of normal vaginal flora to the previously aseptic uterus. The 2nd subtype is endometritis unrelated to pregnancy, which is further subdivided into acute and chronic forms. Pelvic inflammatory disease usually precedes acute endometritis, while the chronic form is often idiopathic but may be associated with chlamydia, tuberculosis, radiation therapy, or intrauterine devices. Clinical features include fever, abdominal pain, abnormal vaginal bleeding, and vaginal discharge. Diagnosis is based on history and physical examination. Imaging is performed to exclude abscesses, septic pelvic thrombophlebitis, and retained products of conception. Management includes hydration and antibiotic therapy.
Tetracyclines are a class of broad-spectrum antibiotics indicated for a wide variety of bacterial infections. These medications bind the 30S ribosomal subunit to inhibit protein synthesis of bacteria. Tetracyclines cover gram-positive and gram-negative organisms, as well as atypical bacteria such as chlamydia, mycoplasma, spirochetes, and even protozoa. The oral absorption of tetracyclines is decreased with the ingestion of some medications and supplements (e.g., milk of magnesia) or food (e.g., dairy products) that contain polyvalent cations, such as calcium and magnesium. Adverse effects include photosensitivity, GI upset, and skin pigmentation in the case of minocycline. Tetracyclines suppress bone growth and discolor teeth in children and are contraindicated in pregnancy and breastfeeding. Of importance, 3 new tetracyclines were approved by the FDA in 2018, which may have a role in treating certain infections due to drug-resistant organisms.
Multiple sclerosis (MS) is a chronic inflammatory autoimmune disease that leads to demyelination of the nerves in the CNS. Young women are more predominantly affected by this most common demyelinating condition. The etiology of MS is unclear; however, both genetic and environmental factors are believed to play a role. The clinical presentation varies widely depending on the site of lesions, but typically includes neurological symptoms that affect vision, motor functions, sensation, and autonomic function. The diagnosis is made via MRI of the entire CNS (brain and spine) as well as CSF examination. Management involves corticosteroids for acute exacerbations and disease-modifying agents to reduce these exacerbations and slow disease progression. The average life expectancy of individuals with MS is decreased by 5–10 years.
Bone marrow, the primary site of hematopoiesis, is found in the cavities of cancellous bones and the medullary canals of long bones. There are 2 types: red marrow (hematopoietic with abundant blood cells) and yellow marrow (predominantly filled with adipocytes). Human marrow composition changes with age. In the young, the entire bone marrow is red, as there is increased blood cell production. As age increases, there is gradual change to the yellow marrow variety. The yellow marrow can revert to red marrow when hematopoiesis is needed (e.g., anemia). The red marrow, by hematopoiesis, produces about 6 billion cells per kilogram per day. The process relies on hematopoietic cells (stem cells and progenitors) producing mature effector cells (lymphocytes, platelets, granulocytes, erythrocytes) with the aid of nonhematopoietic elements. Production is regulated by cytokines released in the bone marrow environment and feedback from target tissues. The marrow structure allows hematopoiesis to take place in the extravascular area, and after staged differentiation, blood cells are released into circulation.
Panic disorder is a condition marked by recurrent and episodic panic attacks that occur abruptly and without a trigger. These episodes are time-limited and present with cardiorespiratory (palpitations, shortness of breath, choking), GI (nausea, abdominal distress), and neurologic (paresthesias, light-headedness) symptoms. Fear of dying or going crazy can occur. Patients may develop agoraphobia (fear of being in places or situations where leaving or escape is difficult). These findings lead to impaired daily functioning. Diagnosing panic disorder is challenging because panic attacks can also occur with other anxiety and mental disorders. Additionally, organic diseases can have similar symptoms. Thorough history and examination, along with a focused workup (based on patient age, risk, and comorbidities) aid in the diagnosis. Management includes both psychotherapy and medications (selective serotonin reuptake inhibitor (SSRIs) and serotonin–norepinephrine reuptake inhibitor (SNRIs)).
Cerebral palsy (CP) refers to a group of conditions resulting in motor impairment affecting tone and posture and limiting physical activity. Cerebral palsy is the most common cause of childhood disability. It is caused by a nonprogressive CNS injury to the fetal or infant brain. It is classified according to muscle tone, its distribution, and the presumed time of injury (spastic diplegia is the most common), and it is present in around 3 per 1,000 live births. Diagnosis is made by a detailed history and physical exam with an MRI scan confirming CNS insult. Interventions are multidisciplinary and prognosis depends on the degree of disability.
Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. Fluid dynamics in the body depend on body fluid compartments, fluid osmolarity, and Starling forces. Edema can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Symptoms vary depending on location of the edema.
The brain and the spinal cord are enveloped by 3 overlapping layers of connective tissue called the meninges. The layers are, from the most external layer to the most internal layer, the dura mater, arachnoid mater, and pia mater. Between these layers are 3 potential spaces called the epidural, subdural, and subarachnoid spaces. The meninges function to protect the contents of the brain and spinal cord. Infection of the CNS presents with inflammation of the meninges, and the etiology can be elicited by examining CSF, which is contained within the subarachnoid space.
Renin-angiotensin-aldosterone system inhibitors constitute an important drug class for the treatment of cardiovascular disease. They are 1st-line antihypertensive agents, in addition to being used in the treatment of MI, heart failure, diabetic nephropathy, and stroke. Renin-angiotensin-aldosterone system inhibitors include ACEis, ARBs, direct renin inhibitors (DRIs), angiotensin receptor and neprilysin inhibitors (ARNIs), and aldosterone antagonists, which affect different components of the RAAS pathway. In general, the use of RAAS inhibitors results in decreased vasoconstriction and serum blood volume. Common adverse effects include hyperkalemia, cough, angioedema, and pancreatitis, which are all more common with the use of ACEis than ARBs.
The hepatitis E virus (HEV) is a small nonenveloped virus that contains linear, single-stranded, positive-sense RNA, making it similar to norovirus. Transmission of HEV is via the fecal–oral route and is clinically similar to that of hepatitis A. However, unlike hepatitis A, hepatitis E is quite severe, especially in pregnant women, and may cause fulminant hepatitis along with hepatic encephalopathy over a period of approximately 8 weeks. Management is mainly preventive and includes avoiding contaminated drinking water, good sanitation, and adequate personal hygiene.
Worldwide, the most frequent cause of death is heart disease. Thus, the common conditions that are evaluated in healthcare facilities are often related to the heart or the cardiovascular system: hypertension, atherosclerotic disease, and heart failure. In radiologic terms, this region is likely the most frequently studied aspect of human anatomy in healthcare delivery settings. Multiple methods are used, including X-ray, CT, MRI, echocardiography, nuclear imaging, and angiography. Each test has its advantages and disadvantages and is obtained on the basis of the clinical presentation, acuity of symptoms, and risks and benefits to the patient. It is important to know the roles of imaging studies to help determine the proper treatment.
The spleen plays a crucial role in immune function, blood filtration, and platelet storage. Asplenia is the absence of splenic tissue or function and can stem from several factors ranging from congenital to iatrogenic. There is a distinction between anatomic asplenia, which is due to the surgical removal of the spleen, and functional asplenia, which is due to a condition that leads to splenic atrophy, infarct, congestion, or infiltrative disease. Howell-Jolly bodies are commonly seen on peripheral blood smear. Abdominal imaging and scintigraphy are used for diagnosis. High risk of sepsis caused by encapsulated bacteria requires adherence to a strict vaccination schedule and early antibiotic treatment when an infection is suspected. Thromboembolic events are common.
Thalassemia is a hereditary cause of microcytic hypochromic anemia and results from a deficiency in either the α or β globin chains, resulting in hemoglobinopathy. The presentation of thalassemia depends on the number of defective chains present and can range from being asymptomatic to rendering the more severely affected patients to be transfusion dependent. The diagnosis can be confirmed using hemoglobin electrophoresis, which will reveal the presence of abnormal α- or β-globin chains.
Nonsteroidal antiinflammatory drugs (NSAIDs) are a class of medications consisting of aspirin, reversible NSAIDs, and selective NSAIDs. NSAIDs are used as antiplatelet, analgesic, antipyretic, and antiinflammatory agents. Common side effects include GI irritation, prolonged bleeding, and AKI.
The primary lymphoid organs, also referred to as central lymphoid/lymphatic organs, are the tissues responsible for the production of lymphoid cells from progenitor cells, incuding the bone marrow and the thymus. In the bone marrow, hematopoietic stem cells progress to become oligopotent progenitors (in the case of lymphocytes, the common lymphoid progenitor). B lymphocytes stay and undergo processes for differentiation before migrating to the secondary lymphoid organs (such as lymph nodes). The progenitor cells that are to become T lymphocytes proceed to the thymus for further maturation.
The secondary lymphoid organs, also called peripheral lymphoid/lymphatic organs, include MALT, the lymph nodes, and the spleen. These collections of lymphoid tissues provide constant surveillance for pathogens. In their distinct sites, these tissues are filled with immune cells ready to mount a response when antigens are detected. Lymph nodes are seen along lymphatic vessels and occur as chains or groups (neck, groin, axillae, mesenteries, abdomen). MALTs act as immune sensors situated in locations where the lumen is exposed to the external environment (oropharynx, GI tract, genitourinary tract). The spleen is the site of production of antibodies and lymphocytes, but it also aids in the breakdown of platelets and erythrocytes.
The lymphatic system consists of the lymphoid organs containing the cells of the immune system and the lymphatic vessels, which transport interstitial fluid (as lymph) back to the venous circulation. Lymphatic vessels are spread extensively throughout the body, draining and filtering lymph, facilitating homeostasis, and aiding in defense against circulating pathogens. Fluid flow is unidirectional, enabled by valves in the collecting lymphatic vessels. In vessels without valves, the muscle contraction of organs and adjacent blood vessels help in the fluid movement. To return to the venous circulation, the lymph is collected by the major lymphatic ducts: right lymphatic duct (collects from the right side of the head and neck, the right side of the thorax, and the right upper extremity) and the thoracic duct (collects from the rest of the body). Pathologic conditions involving the lymphatic system are associated with infections, lymphatic damage, or injury and malignancies.
Hypertensive disorders of pregnancy include chronic hypertension, preeclampsia/eclampsia, gestational hypertension, and hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome. These syndromes pose a significant risk to the pregnant woman and her fetus. Hypertension is defined as a BP > 140/90 mm Hg and can be diagnosed before (chronic) or after (gestational) the 20th week of gestation. Preeclampsia is gestational hypertension with proteinuria or end-organ damage. Eclampsia is preeclampsia with seizures. HELLP syndrome is a severe manifestation of preeclampsia leading to hemolysis, low platelets, and liver injury. Management is with antihypertensives and magnesium sulfate for seizure prophylaxis. The definitive treatment for all hypertensive disorders of pregnancy is delivery.
Major neurocognitive disorders (NCDs), also known as dementia, are a group of diseases characterized by decline in a person’s memory and executive function. These disorders are progressive and persistent diseases that are the leading cause of disability among elderly people worldwide. There are several distinct etiologies for major NCDs. While there are known risk factors and measures to prevent major NCDs, there are no effective curative treatments.
Infertility is the inability to conceive in the context of regular intercourse. The most common causes of infertility in women are related to ovulatory dysfunction or tubal obstruction, whereas, in men, abnormal sperm is a common cause. Diagnosis of infertility involves laboratory assessments for ovulatory function and a hysterosalpingogram to determine tubal patency in women, and semen analysis to assess the condition in men. Management involves treatment of the underlying pathology when possible, and may include ovulation induction with either timed intercourse or intrauterine insemination (IUI), in vitro fertilization (IVF), and donor gametes, or by gestational surrogates or adoption.
Delirium is a medical condition characterized by acute disturbances in attention and awareness. Symptoms may fluctuate during the course of a day and involve memory deficits and disorientation. There are many causes of delirium. Early recognition and accurate diagnosis constitute the 1st steps to adequate management. The primary goal of treatment is to identify and reverse the underlying cause and prevent future episodes. Pharmacotherapy is reserved for the most severe cases of agitation.
Renal cell carcinoma (RCC) is a tumor that arises from the lining of the renal tubular system within the renal cortex. Renal cell carcinoma is responsible for 80%–85% of all primary renal neoplasms. Most RCCs arise sporadically, but smoking, hypertension, and obesity are linked to its development. The disease usually presents asymptomatically. When symptoms finally arise, the tumor has already grown significantly and/or spread to other tissues. The classic clinical triad of RCC is flank pain, hematuria, and a palpable abdominal renal mass, but this triad appears in only about 9% of cases. Affected individuals also commonly present with fever and/or anemia. Renal cell carcinoma is usually diagnosed via CT scan of the abdomen and pelvis. Localized cases of RCC are commonly treated and cured with surgery, and advanced cases are treated with a combination of immunotherapy and/or molecular targeted therapy. The long-term prognosis for locally advanced or metastatic RCC is often poor.
The glycopeptide antibiotics (GPAs) vancomycin and teicoplanin are inhibitors of bacterial cell wall synthesis and considered the last resort treatment of severe infections due to gram-positive bacteria such as Staphylococcus aureus, Enterococcus spp., and Clostridiodes difficile. Vancomycin is the only GPA available in the United States. The medication has poor absorption in the GI tract; therefore, oral vancomycin is used for infections of the intestinal lumen including C. difficile. Intravenous vancomycin is indicated for severe gram-positive infections including endocarditis, pneumonia, and bacteremia. Significant adverse effects include anaphylaxis, hypersensitivity reactions, red man syndrome (related to rapid infusion), nephrotoxicity, and ototoxicity.
The sulfonamides are a class of antimicrobial drugs inhibiting folic acid synthesize in pathogens. The prototypical drug in the class is sulfamethoxazole. Although not technically sulfonamides, trimethoprim, dapsone, and pyrimethamine are also important antimicrobial agents inhibiting folic acid synthesis. The agents are often combined with sulfonamides, resulting in a synergistic effect. The primary indication for use is treatment of urinary tract infection (although significant resistance has emerged). In addition, the drugs are used to treat and prevent opportunistic infections such as toxoplasmosis encephalitis and pneumocystis pneumonia in immunosuppressed individuals. The most common adverse events are hypersensitivity reactions, fever, rash, GI upset, and hematologic reactions. The drugs are generally contraindicated in pregnancy, young/ill infants, and individuals with megaloblastic anemia or severe renal impairment.
Ovarian cysts are defined as collections of fluid or semiliquid material, often walled off by a membrane, located in the ovary. These cysts are broadly categorized as either functional or neoplastic. Neoplastic ovarian cysts are subcategorized as either benign or malignant. When the cysts occur as a result of normal physiologic processes, they are called functional, whereas if there is abnormal growth of ovarian cells, the cyst is referred to as neoplastic. In women of reproductive age, neoplastic ovarian cysts are typically benign; however, the risk of malignancy increases in the postmenopausal period. While most ovarian cysts do not cause symptoms, some women report vague symptoms such as lower abdominal pain or abdominal fullness. Complications of functional cysts include torsion and rupture. Neoplastic cysts may be either benign or cancerous. A diagnosis of ovarian cancer requires consultation with a specialist because treatment involves coordination of surgery and chemotherapy. Treatment is dependent on the etiology of the ovarian cyst and may range from surgical intervention to supportive care only.
Pregnancy is the time period between fertilization of an oocyte and delivery of a fetus approximately 9 months later. The 1st sign of pregnancy is typically a missed menstrual period, after which, pregnancy should be confirmed clinically based on a positive β-hCG test (typically a qualitative urine test) and pelvic ultrasound. There are numerous maternal adaptations to pregnancy, both anatomic and physiologic, which occur to help support the developing fetus and prepare the mother's body for ultimate delivery. Pregnancy is not a pathologic condition, but good routine prenatal care can help achieve the best outcomes for both the mother and infant. Prenatal care includes appropriate lab and ultrasound testing, anticipatory guidance, and offering solutions or advice for common pregnancy discomforts.
Pancreatic cancer, consisting mostly of invasive pancreatic ductal adenocarcinoma (PDAC), arises from the ductal cells of the exocrine pancreas and is the 4th leading cause of cancer-related deaths in the United States. Pancreatic cancer has the highest mortality rate among the major cancers, with a 5-year survival rate of only 8%–10%. Clinical presentation includes symptoms of abdominal pain, jaundice, and weight loss. Diagnosis is made by CT, MRI, and endoscopic ultrasonography (EUS). Management by surgical resection, usually with neoadjuvant or adjuvant chemotherapy, provides the only chance for cure in the 15%–20% of patients who have resectable disease at the time of diagnosis. Other rare malignant tumors arising from the exocrine pancreas are acinar cell carcinoma and pancreatoblastoma.
Hypokalemia is defined as plasma potassium (K+) concentration < 3.5 mEq/L. Homeostatic mechanisms maintain plasma concentration between 3.5–5.2 mEq/L despite marked variation in dietary intake. Hypokalemia can be due to renal losses, GI losses, transcellular shifts, or poor dietary intake. If minor in severity, hypokalemia is usually asymptomatic. However, acute reductions in K+ level or severe hypokalemia can lead to cardiac arrhythmias, muscle weakness, rhabdomyolysis, paralysis, and respiratory failure. Diagnosis is by clinical history and lab testing. Management is guided by severity and includes treating urgent symptoms, replacing the K+ deficit, and treating the underlying cause.
The hepatitis A virus (HAV) is a nonenveloped virus of the Picornaviridae family with single-stranded RNA. The virus replicates in the liver, is excreted in the bile, and is found in high concentrations in the stool of acutely infected individuals. The 2 main routes of infection are consumption of contaminated food or water and direct contact with an infected person. HAV causes an acute, highly contagious hepatitis with unspecific prodromal symptoms such as fever and malaise followed by jaundice and elevated liver transaminases. Most individuals recover fully within a few months, and the immunity resulting from HAV infection is lifelong. Unlike hepatitis B and C, HAV infection does not result in chronic infection or chronic liver disease. Preventive vaccination is available for HAV and is recommended for individuals with increased risk of exposure and, in some countries such as the United States, for all children > 12 months of age.
Although hypertension is defined as a blood pressure of > 130/80 mm Hg, individuals can present with comorbidities of severe asymptomatic or “uncontrolled” hypertension (≥ 180 mm Hg systolic and/or ≥ 120 mm Hg diastolic) that carries with it a significant risk of morbidity and mortality. Despite the prolonged presence of hypertension, there may be no signs or symptoms of end-organ damage (e.g., brain, eyes, heart, kidneys) until function becomes decompensated or severely impaired. Individuals may present with clinical symptoms such as chest pain due to MI or focal neurologic changes associated with a cerebral infarction or intracranial hemorrhage. Diagnosis is made using serial blood pressure measurements and testing for end-organ damage. Management includes lowering the blood pressure and treating specific organ damage.
The 4 pair of paranasal sinuses include the maxillary, ethmoid, sphenoid, and frontal sinuses. The sinuses are a group of air-filled cavities located within the facial and cranial skeleton; all are connected to the main nasal cavity and nasopharynx. Functions include contributing to voice resonance, reducing the skull weight to facilitate an upright head position, conditioning (warming and humidifying) inhaled air, and maximizing the surface of the nasal mucosa.
Acute kidney injury refers to sudden and often reversible loss of renal function, which develops over days or weeks. Azotemia refers to elevated levels of nitrogen-containing substances in the blood that accompany AKI, which include BUN and creatinine. Uremia refers specifically to the constellation of symptoms that occur with severe renal dysfunction. The etiologies of AKI are classified as prerenal, intrinsic renal, or post-renal, and there is a varied clinical presentation depending on the severity of kidney dysfunction. Acute kidney injury is diagnosed initially by a change in serum creatinine levels, and then the etiology is determined by clinical history, lab testing, imaging, and possibly kidney biopsy. The management of AKI depends on the etiology; however, attention to the individual's volume status and serum electrolytes is always important. If management is unsuccessful and AKI progresses to CKD, then renal replacement therapy with dialysis or kidney transplantation is necessary.
Colon polyps are growths of mucosal tissue in the colon, the most common site of polyps in the GI tract. Polyps can be classified as neoplastic or nonneoplastic and may be associated with genetic syndromes. Hyperplastic polyps are nonneoplastic and are the most common type overall, whereas adenomas are the most common type of neoplastic polyp and have the potential to progress to cancer. For most people without hereditary syndromes, colon cancer screening should begin at age 50 (at age 45 for Black individuals) and in adolescence for those with the rare familial adenomatous polyposis (FAP) syndrome. Diagnosis is by biopsy, and management includes frequent surveillance in people with adenomatous polyps or screening every 10 years in the general population until age 75.
Tension headache is the most common of the primary primary headache disorders and one of the most common disorders presenting for medical evaluation worldwide. Tension headaches are generally described as bilateral, nonthrobbing, and of mild to moderate severity. There is no aura or other associated features. The diagnosis is clinical, often self-diagnosed by the patient or in the primary care setting. Management consists of abortive analgesics, such as NSAIDs and aspirin for isolated attacks, and preventative measures, such as behavioral changes, biofeedback, and preventative administration of medication for more chronic attacks.
Cluster headache is a primary headache disorder characterized by moderate-to-severe unilateral headaches that occur in conjunction with autonomic symptoms. Cluster headache can last from weeks to months, during which the affected individual may experience attacks up to several times a day, followed by a pain-free remission period. Autonomic symptoms typically manifest as ocular and nasal phenomena (e.g., ptosis, miosis, nasal congestion, rhinorrhea) on the same side as the headache. Men are more commonly affected by cluster headaches than women. The diagnosis is clinical and often easy to establish owing to the distinct features of the presenting headache. The 1st-line treatment involves administration of oxygen by nasal cannula and/or abortive therapy using a triptan. Preventative strategies (e.g., glucortoicoids, verapamil) are crucial, as cluster headache is a chronic condition associated with significant morbidity and a high rate of suicide.
As the most common cause of dementia, Alzheimer disease affects not only many individuals but also their families. Alzheimer disease is a progressive neurodegenerative disease that causes brain atrophy and presents with a decline in memory, cognition, and social skills. Several genetic defects and risk factors have been described, although there is no clear cause in the majority of cases. The main pathologic features are neuritic plaques, extracellular deposits of amyloid peptides, and neurofibrillary tangles. The clinical features are memory impairment, loss of executive function and judgment, impaired cognitive function, and behavioral changes. Diagnosis is based on clinical examination, neuropsychiatric testing, and imaging. There is no curative therapy, but symptomatic management with medications may slow progression; these include cholinesterase inhibitors, the N-methyl-D-aspartate (NMDA) receptor antagonist memantine, and a recently approved anti-amyloid monoclonal antibody.
Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. The work of hormones allows the body to maintain homeostasis and regulate growth and development. Hormones are typically either made from amino acids or derived from cholesterol (the latter group being known as steroid hormones). Hormones exert their effects by binding to receptors either on the cell surface (most amino acid–based hormones) or within the cytosol (steroid hormones). Ultimately, binding to receptors triggers changes in gene expression or enzymatic activity within the cell.
A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Diagnosis is clinical, relying on history and physical exam, but also may use EEG and other tools. Management includes both abortive and preventive medications but may not be required in self-limited cases with no etiology found during workup.
Antidiarrheal agents include several drug classes, including opioid agonists, somatostatin analogues, adsorbents, and bile acid sequestrants. These medications mainly work through antimotility and/or antisecretory effects. Somatostatin analogues are particularly helpful for secretory diarrhea due to endocrine hormone-producing malignancies, while bile acid sequestrants can be used for conditions causing bile acid malabsorption diarrhea. Antidiarrheals can decrease the clearance of infectious pathogens and toxins and should be avoided in invasive infectious diarrhea.
Obstetric imaging refers to imaging of the female reproductive tract and developing fetus during pregnancy. Ultrasonography is the 1st-line imaging modality during pregnancy as it does not emit radiation; thus, it is the safest option for the developing fetus. Obstetricians depend heavily on ultrasound for the detection, monitoring, and assessment of several maternal and fetal conditions without radiation exposure. For example, congenital fetal anomalies, abnormal placentation, poor fetal growth, and abnormal fluid volumes can all be thoroughly assessed using ultrasound. Radiation-emitting imaging modalities (X-ray, CT) are typically reserved for nonobstetric emergency situations.
Focused assessment with sonography for trauma is a point-of-care ultrasound examination protocol for the abdominal and thoracic cavities performed in the emergency room as part of the secondary survey in advanced trauma life support. The main goal of the FAST exam is to identify free intraperitoneal fluid (blood) and pericardial effusion from trauma. As FAST requires only an ultrasound machine at the bedside and an experienced sonographer, it is widely available, quicker, and less invasive than other image modalities. Focused assessment with sonography for trauma has largely replaced diagnostic peritoneal lavage.
Parkinson's disease (PD) is a chronic, progressive neurodegenerative disorder. Although the cause is unknown, several genetic and environmental risk factors are currently being studied. Individuals present clinically with resting tremor, bradykinesia, rigidity, and postural instability. Parkinson disease is diagnosed clinically on the basis of characteristic signs and symptoms. The postmortem finding of Lewy bodies in the brain is the only confirmation for the disease. Treatment includes supportive physical and emotional care plus medications such as levodopa/carbidopa, monoamine oxidase type B inhibitors, and dopamine agonists.
An ischemic stroke (also known as cerebrovascular accident) is an acute neurologic injury that occurs as a result of brain ischemia; this condition may be due to cerebral blood vessel occlusion by thrombosis or embolism, or rarely due to systemic hypoperfusion. The clinical presentation includes neurologic symptoms with varying degrees of motor and sensory loss corresponding to the area of the brain that is affected and the extent of tissue damage. Diagnosis is made by physical examination and imaging. Management is ideally with thrombolytic therapy to restore blood flow, depending on the time frame and clinical situation. Long-term rehabilitation with physical, occupational, and speech therapies is important after the acute event.
Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Because the matrix is mineralized (rather than aqueous), nutrients and waste cannot diffuse through the matrix. Bone has developed a unique structure to allow the functions to occur. The structure of bone allows the bone to be hard, but not too brittle, and gives bone the strength to resist compressive and bending forces. As a result, bone is ideally suited for the functions of support, protection of vital organs, and movement. In addition, bone produces blood cells in the marrow and is the body's primary storage site for calcium.
Migraine headache is a primary headache disorder and is among the most prevalent disorders in the world. Migraine is characterized by episodic, moderate to severe headaches that may be associated with increased sensitivity to light and sound, as well as nausea and/or vomiting. A migraine attack might be preceded by a so-called aura—neurologic phenomena of visual, auditory, sensual, or motor quality. There is a strong hereditary component in the etiology of migraines. Migraine headache is a clinical diagnosis with several variants. Management strategies include abortive therapy such as NSAIDs and triptans to manage acute episodes as well as preventive strategies to minimize morbidity and pain-related disability.
Vasculitides are a group of conditions characterized by vasculitis, ischemia, and damage to the organs supplied by the affected vessels. The affected arteries are of different sizes and locations and vary by the type of vasculitis. Vasculitides can be a primary condition or secondary to another underlying disease. There is no clearly known pathophysiology. The diagnosis should be considered in any individual with palpable purpura, pulmonary infiltrates, ischemic events, and multisystem disease. Prompt recognition and therapy of the vasculitides are imperative, as they are often serious and sometimes fatal diseases. Management includes immunosuppressive, antiviral, and/or antiinflammatory agents.
Ventricular tachycardia is any heart rhythm faster than 100 beats/min, with 3 or more irregular beats in a row, arising distal to the bundle of His. Ventricular tachycardia is the most common form of wide-complex tachycardia, and it is associated with a high mortality rate. Ventricular tachycardia is often caused by myocardial ischemia, structural disease, congenital conditions, or electrolyte derangement. Individuals may present with chest pain, dyspnea, palpitations, syncope, and hemodynamic instability. Diagnosis is based on characteristic ECG findings of wide-complex QRS, fusion, and capture beats. Management may require antiarrhythmic medications or electrical cardioversion to avoid complications such as heart failure, multiorgan failure, and cardiac arrest.
The 2 primary thyroid hormones are triiodothyronine (T3) and thyroxine (T4). These hormones are synthesized and secreted by the thyroid, and they are responsible for stimulating metabolism in most cells of the body. Their secretion is regulated primarily by thyroid-stimulating hormone (TSH), which is produced by the pituitary gland. Thyroid-stimulating hormone is regulated by thyroid-releasing hormone (TRH; which is stimulatory) and somatostatin (which is inhibitory). Both of these hormones are produced by the hypothalamus. T3 is far more active than T4, so most T4 is converted to T3 in the periphery (e.g., liver). T3 helps to maintain normal cellular metabolism, oxygen consumption, energy levels, heart rate, thermoregulation, bowel movements, mental health, and neurologic function. Abnormalities in thyroid hormone levels can lead to hyperthyroidism and hypothyroidism.
Hepatitis D virus (HDV) is a small enveloped, single-stranded RNA virus. Hepatitis D virus is considered a satellite virus, as it requires the presence of hepatitis B virus (HBV) for assembly and secretion. Therefore, in order for an individual to contract hepatitis D, coinfection or superinfection with HBV is required. Like HBV, HDV is transmitted parenterally, through unprotected sexual intercourse, or perinatally. Clinical presentation is that of a classical viral hepatitis, including coinfection of HDV and HBV, which is considered the most serious form of hepatitis because of the high mortality rate. For acute cases, management is supportive, whereas for chronic cases, pegylated interferon alfa (PEG-IFN-α) is needed.
Huntington disease (HD) is a progressive neurodegenerative disorder with an autosomal dominant mode of inheritance and poor prognosis. It is caused by cytosine-adenine-guanine (CAG) trinucleotide repeats in the huntingtin gene (HTT). The most common clinical presentation in adulthood is a movement disorder known as chorea: abrupt, involuntary movements of the face, trunk, and limbs. Psychiatric and cognitive features are also characteristic, and patients with HD are at an increased risk for suicide throughout the course of the disease. The diagnosis is primarily clinical, often with a positive family history followed by genetic confirmation. Management by an interdisciplinary team is supportive, with the goal of maintaining quality of life. Treatment of depression, agitation, and psychosis is the 1st priority for patients with Huntington disease over the treatment of chorea.
Transient ischemic attack (TIA) is a temporary episode of neurologic dysfunction caused by ischemia without infarction that resolves completely when blood supply is restored. Transient ischemic attack is a neurologic emergency that warrants urgent medical attention. A “tissue-based” definition is currently used rather than the former time-based limit of symptoms lasting less than 24 hours. The causes of TIA may be small clots or thromboemboli imposed on a blood vessel compromised by atherosclerosis, inflammation, or amyloid; inadequate cerebral blood flow from vasoconstriction; or severe hypotension. The clinical presentation includes transient neurologic deficits that resolve spontaneously. Management includes the reduction of risk factors to decrease the risk of a future stroke.
Brain death is a legal and clinical term describing the irreversible cessation of all cerebral and brainstem functions, including the ability of the brain stem to regulate vegetative and respiratory activities. Brain death can be due to a variety of etiologies causing catastrophic injuries to the brain, including brain ischemia due to cardiopulmonary arrest, drugs, sepsis, and trauma. The diagnosis is made at the bedside based on the clinical context and performance of a neurological exam. Additional ancillary studies may be needed to support the diagnosis and diagnostic criteria may vary among states and countries. A diagnosis of brain death must be established prior to consideration of organ donation.
Epilepsy is a chronic brain disorder marked by recurrent and unprovoked seizures. These seizures can be classified as focal or generalized and idiopathic or secondary to another condition. Clinical presentation correlates to the classification of the epileptic disorder. Diagnosis is confirmed with EEG. While some epileptic disorders resolve over time, many require lifelong antiepileptic medication for management or, in some refractory cases, surgical procedures.
Meningitis is inflammation of the meninges around the brain and spinal cord. The majority of cases occur during childhood and are predominantly viral or bacterial in etiology. Clinical presentation is influenced by the age of the child and the causative pathogen, but meningitis typically presents with signs of meningeal irritation, fever, and lethargy. Management varies depending on the pathogen and is isolated to the CSF. Prognosis is dependent on the causative pathogen and appropriate timely intervention. Bacterial meningitis can be life-threatening and has severe complications that may result in long-term sequelae.
The pituitary gland, also known as the hypophysis, is considered the “master endocrine gland” because it releases hormones that regulate the activity of multiple major endocrine organs in the body. The gland sits on the sella turcica, just below the hypothalamus, which is the primary regulator of the pituitary gland. The pituitary gland has 2 lobes: the anterior lobe (the adenohypophysis) and the posterior lobe (the neurohypophysis). Each lobe has its own regulation, set of secretory products, and feedback loops. Abnormalities in the pituitary gland can lead to a wide range of clinical conditions, some of which include hyperprolactinemia, acromegaly, hyperthyroidism or hypothyroidism, and central diabetes insipidus.
Lateral medullary syndrome (also known as Wallenberg syndrome, posterior inferior cerebellar artery (PICA) syndrome, and vertebral artery syndrome) is a neurological constellation of symptoms and signs due to obstruction in vessels supplying the medulla, resulting in brainstem ischemia or infarction. The most common cause is atherosclerosis in the posterior cerebral circulation, and the most reported symptom is a transient ischemic attack (TIA) with dizziness or vertigo. With stroke/infarction, patients also present with nausea and vomiting, loss of balance with gait, instability, hoarseness, and difficulty in swallowing. The signs are dependent on the specific nuclei and fibers affected. Diagnosis is made by clinical exam and imaging with CT/MRI. Management is mostly supportive, including speech and occupational therapy after acute intervention, as well as risk factor reduction for future ischemic events.
Pyelonephritis is infection affecting the renal pelvis and the renal parenchyma. This condition arises mostly as a complication of bladder infection that ascends to the upper urinary tract. Pyelonephritis can be acute or chronic (which results from persistent or chronic infections). Typical acute symptoms are flank pain, fever, and nausea with vomiting. The chronic type depends on the underlying pathology. The diagnosis is established via clinical presentation, supported by laboratory findings (in blood and urine). Imaging studies are performed if severe illness is noted or there is no response to initial treatment (antibiotics). CT is the study of choice, given its ability to detect renal abnormalities associated with the infection, including the extent of the disease. Perinephric abscess is an infection involving the perinephric space between the kidney and Gerota’s fascia. Perinephric abscess can be an extension from pyelonephritis or from hematogenous spread of a systemic infection. The diagnosis is established via CT scan. The treatment includes antibiotics, with abscess drainage (which is both diagnostic and therapeutic).
High-risk headaches, sometimes also referred to as red-flag headaches, encompass secondary causes of headache that can result in irreversible end-organ damage, neurologic deficits, loss of vision, and even death. Entities such as subarachnoid hemorrhage, meningitis/encephalitis, and intracranial tumors carry high morbidity and mortality risks if not recognized and treated immediately. Diagnosis of a high-risk headache requires a high degree of clinical suspicion and is made by conducting a thorough clinical evaluation followed by a targeted workup for the most likely etiology. Management depends on the etiology but consists of prompt treatment of the underlying cause and stabilization of accompanying organ dysfunction.
Movement disorders can be characterized as hypokinetic or hyperkinetic and often require pharmacologic management to improve the individual’s level of function. Common movement disorders include essential tremor, tics (Tourette syndrome), Parkinson disease, Huntington disease, and Wilson disease. Each of these conditions requires unique pharmacologic interventions depending on the pathophysiology and symptom severity. For example, Parkinson disease requires restoration of dopaminergic activity, while symptoms of Huntington disease are ameliorated by reducing dopamine concentrations. Although these agents can be highly beneficial, no agent is innocuous and some have potentially severe adverse events.
Chest pain is one of the most common and challenging complaints that may present in an inpatient and outpatient setting. The differential diagnosis of chest pain is large and includes cardiac, gastrointestinal, pulmonary, musculoskeletal, and psychiatric etiologies. When you encounter a patient with chest pain, eliminating life-threatening causes, such as acute coronary syndrome (ACS) and pulmonary embolism, should be a priority. A thorough history and examination should be performed to narrow the differential diagnosis and guide diagnostic workup and management.
The process of bone formation is called ossification. The 2 types of ossification are intramembranous ossification, in which bone is developed directly from mesenchyme cells, and endochondral ossification, in which a hyaline cartilage model is created 1st and then later replaced with bone. Bone continues to grow into early adulthood at the epiphyseal plates, where chondrocytes continue to divide, die, and be replaced with mineralized bone. Bone mineralization occurs because the osteoblasts allow high levels of calcium and phosphate to accumulate above critical threshold levels within bone.
The hypothalamic and pituitary hormones are the most important regulators of the endocrine system. The hypothalamus functions as the coordinating center between the CNS and endocrine system by integrating the signals received from the rest of the brain and releasing appropriate regulatory hormones to the pituitary gland. The pituitary gland then releases its own hormones in response to hypothalamic stimulation. Pituitary hormones regulate multiple endocrine organs, including the gonads, thyroid gland, adrenal glands, and mammary glands. Pituitary hormones also play a critical role in growth and water balance.
Class 2 antiarrhythmics include beta-blockers, which exert their therapeutic effects by blocking epinephrine and norepinephrine from binding to the beta-adrenergic receptors in cardiac tissue. The outcome is an antiarrhythmic effect, which results from decreased sinoatrial node activity and increased atrioventricular conduction time and refractory period. Additional effects include decreased cardiac contractility, afterload, and blood pressure. Class 2 antiarrhythmics are used in the management of atrial fibrillation, atrial flutter, supraventricular tachycardia, and ventricular arrhythmias. Adverse effects include bradycardia, hypotension, bronchospasm, fluid retention, and fatigue. Beta-blockers should not be used in individuals with decompensated heart failure, shock, and severe bradycardia.
The hypothalamus is a collection of various nuclei within the diencephalon in the center of the brain. The hypothalamus plays a vital role in endocrine regulation as the primary regulator of the pituitary gland, and it is the major point of integration between the central nervous and endocrine systems. Different nuclei within the hypothalamus play roles in hormone regulation and secretion, autonomic regulation, thermoregulation, food and water intake, sleep and circadian rhythms, memory, and emotional behavior. The hypothalamus has both neural and circulatory connections with the pituitary gland. Abnormalities in the hypothalamus can lead to a wide range of clinical conditions.
Penetrating abdominal injuries are created by an object puncturing the abdominal wall. Injuries can be high velocity, like gunshot wounds, or low velocity, like stab wounds. Different structures can be injured, including the duodenum, spleen, liver, kidneys, and pelvic organs. The extent and specific type of abdominal traumatic injury can be identified by a proper history and physical exam and supported by appropriate imaging studies. Management, which can be laparotomy or a conservative approach, is dependent on the patient’s hemodynamic stability and specific type of injury.
Antimycobacterial agents represent a diverse group of compounds that have activity against mycobacterial infections, including tuberculosis, leprosy and Mycobacterium avium complex (MAC) disease. The 1st-line agents for tuberculosis are rifampin, isoniazid, pyrazinamide, and ethambutol. The drugs vary in their mechanisms of action: rifampin inhibits RNA synthesis, isoniazid inhibits mycolic acid synthesis, pyrazinamide acts on membrane transport and protein synthesis, and ethambutol prevents cell wall synthesis. Monotherapy is not recommended because of the increased risk of drug resistance. Multidrug treatment takes several months and requires sputum monitoring. As for leprosy, an infection due to Mycobacterium leprae, rifampin is also used, with dapsone. The lepromatous form requires a 3rd agent (clofazimine). Pulmonary infections with MAC are managed with macrolides (azithromycin), rifampin, and ethambutol.
As a general term, headache is a descriptor tied to hundreds of clinical entities. A headache is one of the most common reasons people present for medical attention. All headaches fall into 1 of 2 classification systems; primary and secondary headache syndromes. The presentation, degree of severity, underlying pathogenesis, potential clinical sequelae, management, and prognosis are as variable as the underlying headache entities.
Sturge-Weber syndrome (SWS) is a congenital neurocutaneous disorder presenting with a facial birthmark called a port-wine stain (PWS), neurological abnormalities such as seizures, and eye abnormalities such as glaucoma. Not all of these symptoms have to be present in an affected individual, and some may develop later in life. While the condition is congenital, it is not inherited, as the causative mutation in the gene GNAQ is somatic and sporadic. Diagnosis is suspected based on symptoms and neuroimaging and confirmed with genetic testing. Management is targeted at symptom management and prevention of seizures and hemiparesis.
The pancreas lies mostly posterior to the stomach and extends across the posterior abdominal wall from the duodenum on the right to the spleen on the left. The pancreas is covered with a very thin connective tissue capsule that extends inward as septa, partitioning the gland into lobules. This organ has both exocrine and endocrine tissue. The exocrine portion is organized in grape-like clusters of acini, which are small sacs surrounding the terminal ends of pancreatic ducts. The cells lining the acini and ducts secrete products that make up pancreatic juices, which play a major role in digestion. The endocrine portion of the gland consists of circular islets interspersed between acini, which secrete glucagon, insulin, and somatostatin.
Tuberous sclerosis or tuberous sclerosis complex (TSC) is an autosomal dominant disorder with mainly neurocutaneous symptoms. Mutation in the TSC genes causes excessive tumor-like growths in the brain, eyes, heart, kidney, and lungs. Cutaneous manifestations include hypopigmentation (i.e., ash leaf spots, confetti lesions) or excessive growth (i.e., angiofibroma, shagreen patch). The diagnosis is made on clinical suspicion and confirmed by genetic testing. Management entails a multidisciplinary approach that targets monitoring and treatment of the various manifestations of the disorder. mTOR inhibitors such as sirolimus and everolimus are used to treat severe manifestations.
Spinal muscular atrophy (SMA) is a spectrum of autosomal recessive syndromes characterized by progressive proximal muscle weakness and atrophy, possibly due to degeneration of the anterior horn cells in the spinal cord and motor nuclei in the lower brainstem. There are 5 clinical types of SMA, each with a distinctive clinical presentation unified by motor weakness. The earlier presentations are associated with more severe motor weakness affecting a child’s ability to reach the developmental milestones of sitting or walking. In the more severe types, breathing and swallowing may also become difficult as the disease progresses. The prognosis of SMA is poor. In the less severe types, adults have a normal lifespan. The initial diagnosis is made clinically and confirmed using genetic testing. Management is mostly supportive although novel therapies are being developed. The prognosis depends on the clinical type.
Von Hippel-Lindau (VHL) disease is an autosomal dominant genetic condition resulting from a deletion or mutation in the VHL gene. Individuals diagnosed with VHL disease have tumors and cysts in various parts of their bodies and may present with hemangioblastomas, renal cell carcinoma (RCC), pheochromocytoma, endolymphatic sac tumors of the middle ear, pancreatic tumors, and papillary cystadenomas of the epididymis or the broad ligament. The diagnosis is by genetic testing, laboratory evaluation of BUN, laboratory evaluation for the presence of catecholamines in the blood or urine, fundoscopic exam of the eye to detect hemangioblastoma of the retina, and CT/MRI to detect any other tumors. Management of the disease includes surgical removal of tumors.
The kidneys, solid organs located in the lower back, are extremely important in regulating homeostasis through their role in maintaining blood volume, electrolyte balance, acid–base equilibrium, blood-pressure regulation, and removal of metabolic waste from the blood. Evaluation of renal function and early detection of kidney dysfunction is of primary importance. Tests of renal function are useful in identifying the presence of renal disease, monitoring the response of kidneys to treatment, and determining the progression of renal disease.
The adrenal glands are a pair of retroperitoneal endocrine glands located above the kidneys. The outer parenchyma is called the adrenal cortex and has 3 distinct zones, each with its own secretory products. The outer zona glomerulosa secretes mineralocorticoids (primarily aldosterone); the middle zona fasciculata secretes glucocorticoids (primarily cortisol); and the innermost zona reticularis secretes androgens. Beneath the cortex lies the adrenal medulla, which secretes catecholamines involved in the fight-or-flight response. The medullary cells function more like neurosecretory postsynaptic neurons rather than traditional endocrine cells. The adrenal glands have a rich vascular supply and complex relationships with their surrounding organs.
Coma is defined as a deep state of unarousable unresponsiveness, characterized by a score of 3 points on the GCS. A comatose state can be caused by a multitude of conditions, making the precise epidemiology and prognosis of coma difficult to determine. Diagnosis is made clinically with a thorough neurologic examination, including assessment of the brain stem to evaluate for the presence of brain death. Definitive management depends on the underlying cause.
Shoulder pain is considered chronic when present for > 6 months. Common conditions resulting in chronic shoulder pain include rotator cuff disorders, adhesive capsulitis, shoulder instability, and joint arthritis. Shoulder pain can be intrinsic or extrinsic to the joint. The potential of serious causes of referred pain to the shoulder such as cardiovascular and abdominal etiologies should be considered. A focused history and physical examination is essential and should include inspection, palpation, range of motion (ROM), and provocative testing. Imaging often includes plain radiographs occasionally supplemented with MRI. Management varies related to specific disorders and frequently requires physical therapy.
Locked-in syndrome (LIS) is a rare neurological disorder in which patients are awake and conscious but are unable to move their limbs or speak. The disorder is a result of brain injury to the ventral aspect of the pons and caudal ventral midbrain; etiologies include brainstem stroke, tumors, intracranial bleeding, and demyelinating disorders. Consciousness and the ability to think and reason remain intact, as do the abilities to blink and move the eyes. Diagnosis is made clinically, and the initial management is supportive care for breathing and feeding. Definitive management depends upon the underlying cause and is followed by several months of rehabilitation. Prognosis is generally poor, although some patients are able to achieve significant improvement in some functions.
Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) includes granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA). All 3 diseases cause life-threatening small-vessel vasculitis with a wide range of systemic manifestations, which can involve the lungs, kidneys, skin, and heart. Diagnosis is suspected by clinical presentation and a positive cytoplasmic (c)- or perinuclear (p)-ANCA test. Biopsy of involved tissue confirms the diagnosis. Glucocorticoids and immunosuppressive therapy are the mainstays of treatment.
Bundle branch and fascicular blocks occur when the normal electrical activity in the His-Purkinje system is interrupted. These blocks can be due to many etiologies that may affect the structure of the heart or the conduction system directly. The blocks are classified into right bundle branch block, left bundle branch block, left anterior fascicular block, and left posterior fascicular block depending on the location of the disruption. Most individuals are asymptomatic. ECG will provide the diagnosis. Some common ECG findings include a prolonged QRS interval, R-wave changes, axis deviation, and (in some cases) S-wave changes. No specific treatment is indicated.
Normal pressure hydrocephalus (NPH) is a neurodegenerative disorder characterized by the triad of gait abnormalities, dementia, and urinary urgency or incontinence. Normal pressure hydrocephalus can be either idiopathic or secondary to intraventricular or subarachnoid hemorrhage. Symptoms may be similar to those of Alzheimer and Parkinson's diseases. Diagnosis of NPH is clinical, in addition to lumbar puncture testing and neuroimaging. Management is with surgical shunt placement to drain excess CSF from the cerebral ventricles.
Hypertension, or high blood pressure, is a common disease manifesting as elevated systemic arterial pressure. Hypertension is most often asymptomatic and discovered as part of a routine physical examination, or during triage for an unrelated medical encounter. Age, gender, smoking, obesity, and diet are all contributing factors to hypertension and can lead to heart attack, stroke, congestive heart failure, and CKD if not managed properly. If blood pressure cannot be controlled with lifestyle modifications, medications are employed for the management of hypertension. The 1st-line medication classes include thiazide-like diuretics, angiotensin-converting enzyme inhibitors (ACEis), angiotensin II receptor blockers (ARBs), and calcium channel blockers (CCBs). Contraindications, adverse effects, and drug-to-drug interactions are agent specific.
The scrotum is a sac hanging outside the body that contains parts of the male reproductive system. The scrotum’s main function is to support testicles outside the body so that spermatogenesis can be completed under optimal conditions. The scrotum can be affected by various pathologic conditions, and imaging is a valuable tool in reaching the appropriate diagnosis. The most important imaging method is ultrasonography +/– Doppler mode because scrotal structures are superficial with no intervening gas. MRI is useful when ultrasound is indeterminate.
The small intestine is the longest part of the GI tract, extending from the pyloric orifice of the stomach to the ileocecal junction. The small intestine is the major organ responsible for chemical digestion and absorption of nutrients. The small intestine is divided into 3 segments: the duodenum, the jejunum, and the ileum. Like the entire GI tract, the walls of the small intestine have several layers: an inner absorptive mucosal layer (which is made up of an epithelium, lamina propria, and muscularis mucosa) and submucosal, muscular, and serosal layers. The arterial supply to the small intestine is via branches of the superior mesenteric artery, and veins drain into the hepatic portal system. The small intestine is innervated by the ANS.
The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Bile is secreted by hepatocytes into thin channels called canaliculi. These canaliculi lead into slightly larger interlobular bile ductules, which are part of the portal triads at the “corners” of hepatic lobules. The bile leaves the liver via the right and left hepatic ducts, which join together to form the common hepatic duct. The common hepatic duct joins with the cystic duct to form the common bile duct, which empties into the small intestine. If the sphincters leading into the intestines are closed, bile will travel via the cystic duct into the gallbladder for storage.
Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease, is a sporadic or inherited neurodegenerative disease of upper motor neurons (UMNs) and lower motor neurons (LMNs). Amyotrophic lateral sclerosis is the most common progressive motor neuron disease in North America, primarily affecting men and individuals of Caucasian ethnicity. This disease is characterized by the coexistence of UMN and LMN signs and symptoms. The diagnosis is made clinically. Management is supportive and symptomatic, progressing to end-of-life care.
Central cord syndrome (CCS) is a neurological syndrome caused by an injury to the center of the spinal cord, affecting the spinothalamic tracts ((STTs) sensory) and medial aspect of the corticospinal tracts ((CSTs) motor), most often due to trauma in patients with cervical spondylosis. A less frequent but classic cause of CCS is syringomyelia. Clinical manifestations are motor deficits in the arms more so than the legs and variable sensory deficits below the level of injury. Diagnosis is made clinically and is supported with neuroimaging. Definitive management can be medical or surgical, depending on the severity of the injury. Rehabilitation is the key to maintaining functionality and improving chances of recovery.
Anterior cord syndrome (ACS) is an incomplete cord syndrome predominantly affecting the anterior (ventral) ⅔ of the spinal cord while sparing the dorsal columns. Anterior cord syndrome can be caused by occlusion of the anterior spinal artery or by trauma, which results in disc herniation and bone fragments disrupting the spinal cord. Clinical manifestations include loss of both motor and sensory function below the level of injury. Diagnosis of ACS is by clinical exam and neuroimaging with MRI. Management is directed at resolving the underlying cause. Preservation of motor function is a priority, but the prognosis is poor.
Fibromyalgia is a chronic pain syndrome characterized by widespread body pain, chronic fatigue, mood disturbance, and cognitive disturbance. It also presents with other comorbid symptoms such as migraine headaches, depression, sleep disturbance, and irritable bowel syndrome. Diagnosis is clinical with laboratory exams and imaging reserved to rule out other causes for the spectrum of symptoms. Management is centered around education and lifestyle modification, with both pharmacotherapy (e.g., antidepressants, anticonvulsants) and non-pharmacotherapy (low-impact exercise, cognitive behavioral therapy) showing efficacy.
Ion channel myopathies are a heterogeneous group of disorders that are caused by genetic defects in sodium, chloride, and calcium ion channels in the myocyte membranes resulting in myotonia. These myopathies present clinically with symptoms of muscle pain, weakness, stiffness, cramps, and spasm. Diagnosis is made on the basis of clinical presentation, lab testing, electromyography, and genetic testing. Management involves both prevention with diet and exercise modifications and treatment with diuretics in some cases.
Antiviral agents against influenza are important in preventing and treating influenza infection. Influenza is often self-limited, but high-risk populations suffer significant morbidity and mortality from the illness. Different classes of drugs act on the influenza virus. Neuraminidase inhibitors include oseltamivir (oral), zanamivir (inhalation) and peramivir (IV); these drugs act by inhibiting neuraminidase, the enzyme that cleaves off the new virus particle. By blocking the enzymatic effect, further release of progeny virus to nearby respiratory cells is reduced. Baloxavir, a selective inhibitor of influenza cap-dependent endonuclease, inhibits viral mRNA synthesis. Both neuraminidase inhibitors and baloxavir have activity against influenzas A and B. Adamantanes, or M2 inhibitors, include amantadine and rimantadine, which are active against influenza A but are not often used owing to resistance.
Blood supply to the brain can be divided into an anterior and a posterior circulation, which interconnect to form the circle of Willis. The anterior circulation is derived from the internal carotid arteries and consists mainly of the anterior and middle cerebral arteries. The posterior circulation is derived from the vertebral arteries and consists primarily of the cerebellar and posterior cerebral arteries. The primary venous drainage of the brain occurs via the internal jugular vein.
The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. The colon also contains many mucus-secreting glands to lubricate the stool passing through it. The colon receives its blood supply from colic branches of the superior and inferior mesenteric arteries, which form an important anastomosis along the transverse colon. The colon is regulated by the ANS and receives both sympathetic (inhibitory) and parasympathetic (stimulatory) input.
Anticoagulants are drugs that retard or interrupt the coagulation cascade. The primary classes of available anticoagulants include heparins, vitamin K-dependent antagonists (e.g., warfarin), direct thrombin inhibitors, and factor Xa inhibitors. Anticoagulants are used in the treatment and prevention of thrombotic and embolic diseases including cardioembolic ischemic stroke, acute coronary syndrome, and venous thromboembolism, among other conditions. Patients with atrial fibrillation or thrombophilias may require indefinite or lifelong anticoagulation. Accordingly, the route of administration, drug interactions, pharmacokinetics, and availability of reversal factors should be considered while selecting the anticoagulant therapy.
Acute otitis media is an infection in the middle ear characterized by mucosal inflammation and retention of fluid. The most common pathogens are Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. The condition can present with fever, otalgia, and diminished hearing. Diagnosis is made by history and otoscopic exam showing a bulging tympanic membrane with reduced mobility. Observation or antibiotics are the usual management approaches, but surgery for tympanostomy tubes may be required if there are recurrent infections. Potential complications include hearing loss, tympanic membrane perforation, and mastoiditis.
Giant cell arteritis (GCA), also known as temporal arteritis, is a type of large-vessel vasculitis that predominantly affects the aorta and its major branches, with a predilection for the branches of the carotid (including the temporal artery). Giant cell arteritis is defined by inflammatory leukocytes in the vessel walls leading to reactive damage, ischemia, and necrosis. Giant cell arteritis causes headaches, scalp tenderness, jaw pain, vision problems, and potentially blindness. The diagnosis is made with temporal artery biopsy. Prompt treatment with glucocorticoids can relieve symptoms and prevent vision loss.
Pulmonary edema is a condition caused by excess fluid within the lung parenchyma and alveoli as a consequence of a disease process. Based on etiology, pulmonary edema is classified as cardiogenic or noncardiogenic. Patients may present with progressive dyspnea, orthopnea, cough, or respiratory failure. Pulmonary edema is easily recognized on a chest X-ray, and an evaluation should be done to identify the underlying cause. Management involves supporting the patient’s respiratory status with oxygen, diuretics, and treatment of the underlying cause.
Encephalitis is inflammation of the brain parenchyma caused by an infection, usually viral. Encephalitis may present with mild symptoms such as headache, fever, fatigue, and muscle and joint pain or with severe symptoms such as seizures, altered consciousness, and paralysis. The diagnosis is based on clinical suspicion, and once suspected, immediate empiric treatment is warranted to prevent catastrophic and long-term neurologic sequelae. Encephalitis is managed with supportive measures and antiviral therapy. Focal neurologic defects are common after encephalitis, and hence, physiotherapy is usually required.
Seizures occur when uncontrolled excessive synchronous neuronal activity in the brain causes sudden transient changes in motor function, sensation, behavior, or mental status. Seizures are classified primarily as generalized or focal and may occur once or be recurrent (epilepsy). Prolonged or recurrent seizures lasting > 30 minutes are called status epilepticus. Diagnosis depends on thorough history, physical exam, and EEG findings. Treatment is directed at the underlying trigger, and medications are administered as necessary. Most children that seize recover without any sequelae, but prognosis depends on the initial cause and the presence of underlying neurologic pathology.
Acute respiratory distress syndrome is characterized by the sudden onset of hypoxemia and bilateral pulmonary edema without cardiac failure. Sepsis is the most common cause of ARDS. The underlying mechanism and histologic correlate is diffuse alveolar damage (DAD). Diffuse alveolar damage involves damage to the endothelial and alveolar epithelial cells and is associated with inflammation and the development of hyaline membranes lining the inner alveolar walls. The reparative stage follows after weeks, with fibrosis possibly occurring later. Clinically, the following triad of findings favors a diagnosis of ARDS: acute or rapidly progressive dyspnea, hypoxic respiratory failure (partial pressure of O2/fraction of inspired O2 ratio < 300 mm Hg), and bilateral alveolar opacities on chest imaging. Management involves determination and treatment of the cause while providing adequate oxygen, reducing further lung damage, and avoiding fluid overload. Most patients require mechanical ventilation. Acute respiratory distress syndrome is associated with high mortality or long-term complications potentially developing even after treatment.
Atelectasis is the partial or complete collapse of a part of the lung. Atelectasis is almost always a secondary phenomenon from conditions causing bronchial obstruction, external compression, surfactant deficiency, or scarring. Hypoxemia can occur as a result of blood flowing through unventilated lung segments. Patients are often asymptomatic. However, dyspnea, cough, chest pain, and fever can also occur. The diagnosis is made with imaging. Management includes treatment of the underlying etiology, lung expansion exercises, chest physiotherapy, bronchodilators, and bronchoscopy in select cases.
Urinary tract infections (UTIs) represent a wide spectrum of diseases, from self-limiting simple cystitis to severe pyelonephritis that can result in sepsis and death. Urinary tract infections are most commonly caused by Escherichia coli, but may also be caused by other bacteria and fungi. Depending on the location of the infection, patients can present with dysuria, urinary urgency, increased urinary frequency, suprapubic pain, and fever. Urinalysis and urine culture along with the clinical presentation help in the diagnosis of UTIs. Management options include oral or IV antibiotics such as trimethoprim-sulfamethoxazole, nitrofurantoin, and ceftriaxone. In certain instances, further workup may be needed to determine the underlying conditions that predispose an individual to UTIs.
Hemoptysis is defined as the expectoration of blood originating in the lower respiratory tract. Hemoptysis is a consequence of another disease process and can be classified as either life threatening or non-life threatening. Only 5%–15% of patients with hemoptysis have life-threatening bleeding. However, hemoptysis can result in significant morbidity and mortality due to both drowning (reduced gas exchange as the lungs fill with blood) and hemorrhagic shock. The most common causes of hemoptysis include bronchiectasis, lung cancer, tuberculosis, and aspergillosis. Diagnosis involves chest imaging and bronchoscopy. In cases of life-threatening bleeding, treatment is initially directed at stabilizing the patient and, if bleeding is ongoing, hemostasis can often be achieved with minimally invasive techniques (e.g., arterial embolization).
Thrombocytopenia occurs when the platelet count is < 150,000 per microliter. The normal range for platelets is usually 150,000–450,000/µL of whole blood. Thrombocytopenia can be a result of decreased production, increased destruction, or splenic sequestration of platelets. Patients are often asymptomatic until platelet counts are < 50,000/µL. Clinical manifestations of thrombocytopenia include easy bruising or bleeding, petechiae, purpura, and when severe, spontaneous mucosal and/or internal bleeding. Diagnosis is made with a CBC and blood smear; additional testing may be required to determine the underlying etiology if it is not evident from the clinical scenario. Management involves treating the underlying etiology and platelet transfusions.
Hemostasis refers to the innate, stepwise body processes that occur following vessel injury, resulting in clot formation and cessation of bleeding. Hemostasis occurs in 2 phases, namely, primary and secondary. Primary hemostasis involves platelet adhesion, activation, and aggregation to the damaged vascular endothelium, forming a plug that stops the bleeding temporarily. Secondary hemostasis involves the activation of the coagulation cascade resulting in the formation of a more stable plug. Finally, as the vasculature is repaired, the clot is broken down in the fibrinolytic phase.
Botulism is a rare, neuroparalytic syndrome caused by Clostridium botulinum (C. botulinum). A fatal neurotoxin (botulinum toxin) is released causing varying degrees of muscle paralysis and distinct clinical syndromes. The most common types of botulism are foodborne and infant. Botulism presents with blurred vision, respiratory failure, and symmetric, descending flaccid paralysis. Characterization includes intact sensorium, normal heart rate and blood pressure, absence of fever, and absence of sensory deficits. Diagnosis is made on clinical grounds and can be confirmed by the isolation of bacteria or toxins from stool, wound specimens, or food sources. The approach to managing a case of botulism should include prompt management of respiratory failure, administration of antitoxin, and supportive care for paralysis.
Computed tomography (CT) is one of the most commonly used imaging methods because it is widely available, fast, and reliable. CT scans deploy X-rays to obtain cross-sectional images of the body. A CT scanner consists of a tube that rotates around the patient and emits an X-ray beam and a detector that uses specialized software to receive and convert the beam to an image. The ability to create multiple views (axial, sagittal, coronal) and use contrast (intravenous, oral, rectal) allows for enhanced diagnostic yield. Patients are exposed to radiation, and special consideration should be given to patients with a history of iodine allergy, renal disease, or thyroid disease or patients who are pregnant.
Myasthenia gravis (MG) is an autoimmune neuromuscular disorder characterized by weakness and fatigability of skeletal muscles caused by dysfunction/destruction of acetylcholine receptors at the neuromuscular junction. Myasthenia gravis presents with fatigue, ptosis, diplopia, dysphagia, respiratory difficulties, and progressive weakness in the limbs, leading to difficulty in movement. Diagnosis is established based on clinical presentation, detection of antibodies, and electrophysiologic studies. Management is aimed at increasing the activity of acetylcholine at the neuromuscular junction and suppression of antibodies. This disease can be associated with thymomas and thymic hyperplasia, and thymectomy is sometimes indicated. Myasthenia gravis can progress to a life-threatening cholinergic crisis with respiratory failure, but this is preventable with appropriate management. Prognosis is generally good with treatment, and some patients can achieve a long-term remission.
Hyperkalemia is defined as a serum potassium (K+) concentration > 5.2 mEq/L. Homeostatic mechanisms maintain the serum K+ concentration between 3.5 and 5.2 mEq/L, despite marked variation in dietary intake. Hyperkalemia can be due to a variety of causes, which include transcellular shifts, tissue breakdown, inadequate renal excretion, and drugs. Hyperkalemia is usually asymptomatic if minor in severity; however, acute elevations or severe hyperkalemia can lead to potentially fatal cardiac arrhythmias. Management is guided by severity and includes measures to stabilize the myocardial membrane potential, transiently shifting K+ intracellularly, removing K+ from the body, and treating the underlying predisposing conditions.
Pulmonary hypertension (PH) or pulmonary arterial hypertension (PAH) is characterized by elevated pulmonary arterial pressure, which can lead to chronic progressive right heart failure. Pulmonary hypertension is grouped into 5 categories based on etiology, which include primary PAH, and PH due to cardiac disease, lung or hypoxic disease, chronic thromboembolic disease, and multifactorial or unclear etiologies. Patients typically present with shortness of breath initially during exercise and then at rest. Diagnosis may involve an echocardiogram, ECG, chest X-ray, pulmonary function tests, a ventilation-perfusion scan, laboratory testing for conditions associated with PAH, and/or cardiac catheterization. Management is often complex and aimed at treating the underlying etiology. Several classes of vasodilatory agents may be used for patients with primary PAH, including calcium channel blockers and vasoactive prostaglandins.
Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. A number of etiologies exist, including diseases of the lungs, cardiovascular, and nervous system. Patients with respiratory failure may present with dyspnea, tachypnea, and altered mentation. The diagnosis is made with arterial blood gas and supplemented with laboratory and imaging studies to elicit an etiology. Management involves treating the underlying cause, supplemental oxygen administration, and mechanical ventilation for severe cases.
Nephrolithiasis is the formation of a stone, or calculus, anywhere along the urinary tract caused by precipitations of solutes in the urine. The most common type of kidney stone is the calcium oxalate stone, but other types include calcium phosphate, struvite (ammonium magnesium phosphate), uric acid, and cystine stones. Nephrolithiasis presents with colicky flank pain, which radiates to the groin, and hematuria due to damage to the ureters. Diagnosis is made by noncontrast CT of the abdomen and pelvis or by renal ultrasound, and urinalysis is performed to exclude concomitant urinary tract infection (UTI). Management depends on the size of the stone. Small stones likely to pass on their own are managed conservatively with hydration and analgesics. Large stones unlikely to pass spontaneously are managed with extracorporeal shock wave lithotripsy (ESWL), ureterorenoscopy, or percutaneous nephrolithotomy. Nephrolithiasis can be complicated by hydronephrosis or acute pyelonephritis. Adequate hydration is the best prophylactic intervention to prevent kidney stones.
Bronchiectasis is a chronic disease of the airways that results from permanent bronchial distortion. This results from a continuous cycle of inflammation, bronchial damage and dilation, impaired clearance of secretions, and recurrent infections. Most cases are idiopathic, though infections, bronchial obstruction, congenital disorders, and systemic conditions can contribute. Patients present with slowly progressive symptoms of cough and sputum production. The diagnosis is made from characteristic radiographic findings, such as bronchial wall thickening and luminal dilatation. Management focuses on improving clearance of mucus, relieving airway obstruction, treating infection, and managing the underlying etiology. Management can include chest physiotherapy, bronchodilators, and antibiotics.
Renal Na+ and water regulation work in tandem to control how fluid is distributed throughout the compartments of the body. Sodium is the body’s dominant extracellular solute, and is responsible for the osmotic force that keeps differing amounts of water in each compartment. Changes in Na+ balance are sensed by the body through changes in blood volume. Changes in water balance are sensed by the body through changes in plasma osmolality. Both ultimately send feedback signals to the kidneys to ensure that homeostasis is maintained. Abnormalities in these processes can result in problems in volume status (e.g., hypertension, pulmonary edema, pitting edema) and dysnatremias (hyponatremia and hypernatremia).
Pericardial effusion is the accumulation of excess fluid in the pericardial space around the heart. The pericardium does not easily expand; thus, rapid fluid accumulation leads to increased pressure around the heart. The increase in pressure restricts cardiac filling, resulting in decreased cardiac output and cardiac tamponade. Signs and symptoms usually occur in the setting of cardiac tamponade and include dyspnea, hypotension, muffled heart sounds, jugular venous distension, and pulsus paradoxus. The diagnosis of pericardial effusion is confirmed with echocardiography. Small effusions in stable patients are treated medically. Larger effusions and cardiac tamponade may require pericardiocentesis or pericardiotomy.
Acute abdomen, which is in many cases a surgical emergency, is the sudden onset of abdominal pain that may be caused by inflammation, infection, perforation, ischemia, or obstruction. The location of the pain, its characteristics, and associated symptoms (e.g., jaundice) are important tools that help narrow the differential diagnosis. Patients will typically have severe tenderness with associated rigidity and rebound tenderness. Laboratory evaluation will demonstrate leukocytosis, acidosis, and in some cases, abnormal hepatic function tests. Imaging helps narrow the differential diagnosis; first-line imaging is always an upright chest X-ray to evaluate for pneumoperitoneum. The treatment and prognosis of acute abdomen strongly depend on the underlying cause, but the vast majority of these cases constitute a surgical emergency with associated morbidity and mortality.
Coronary heart disease (CHD), or ischemic heart disease, describes a situation in which an inadequate supply of blood to the myocardium exists due to a stenosis of the coronary arteries, typically from atherosclerosis. The myocardium becomes ischemic when oxygen supply does not meet oxygen demand. Diagnosis is based on history and ECG findings; cardiac stress tests and catheterizations may also be needed. Treatment is primarily based on reducing the heart's oxygen demand and increasing the delivery of oxygen.
Myocarditis is an inflammatory disease of the myocardium, which may occur alone or in association with a systemic process. There are numerous etiologies of myocarditis, but all lead to inflammation and myocyte injury, most often leading to signs and symptoms of heart failure. The course of myocarditis may vary based on the etiology and timeline of symptom progression. The diagnosis is supported by clinical findings, laboratory evaluation, and cardiac imaging. A definitive diagnosis by endomyocardial biopsy is rarely required. Management is supportive and aimed at addressing complications.
Adrenal insufficiency (AI) is the inadequate production of adrenocortical hormones: glucocorticoids, mineralocorticoids, and adrenal androgens. Primary AI, also called Addison’s disease, is caused by adrenal gland disorder (autoimmune disease, infections, and malignancy, among others). Adrenal insufficiency can also occur because of decreased production of adrenocorticotropic hormone (ACTH) from disease in the pituitary gland (secondary) or hypothalamic disorders and prolonged glucocorticoid therapy (tertiary). Diagnosis is by demonstrating hypocortisolism (via cortisol and ACTH levels and ACTH-stimulation test) and determining the etiology (adrenal autoantibodies, imaging). Glucocorticoid replacement is needed in all forms of AI. Additionally, in primary AI, mineralocorticoid is given to prevent volume depletion, salt loss, and hyperkalemia. Adrenal crisis is a medical emergency; management requires prompt IV hydration and administration of IV glucocorticoids without waiting for initial hormone results.
Atherosclerosis is a common form of arterial disease in which lipid deposition forms a plaque in the blood vessel walls. Atherosclerosis is an incurable disease, for which there are clearly defined risk factors that often can be reduced through a change in lifestyle and behavior of the patient. It manifests itself as vessel stenosis and a source of thromboembolic disease. Its clinical manifestations depend on the specific vessels affected and include most notably coronary artery disease, carotid disease, and peripheral vascular disease. It is the most common primary disease of the arterial vascular system and is responsible for coronary heart disease, the leading cause of death worldwide.
Cardiomyopathy refers to a group of myocardial diseases associated with structural changes of the heart muscles (myocardium) and impaired systolic and/or diastolic function in the absence of other heart disorders (coronary artery disease, hypertension, valvular disease, and congenital heart disease). The list of causes is extensive, ranging from familial disorders to underlying diseases and infections. Patients often present with chest pain, dyspnea, palpitations, and/or syncope. Some patients may be completely asymptomatic, while others may present with sudden cardiac death as the first sign of an underlying condition. Diagnosis is made through the use of ECG and cardiac imaging such as echocardiography and cardiac MRI. Management involves medications typically used to treat heart failure, as well as implantable devices. In severe cases, heart transplantation may be necessary.
Thyroid cancer is a malignancy arising from the thyroid gland cells: thyroid follicular cells (papillary, follicular, and anaplastic carcinomas) and calcitonin-producing C cells (medullary carcinomas). Rare cancers are derived from the lymphocytes (lymphoma) and/or stromal and vascular elements (sarcoma). Driver mutations involving the receptor tyrosine kinase pathway (such as RET and BRAF) and a family history of cancer or related syndromes increase the risk. Exposure to ionizing radiation and iodine deficiency are also considered risk factors. The major types can present as thyroid nodules or enlarged cervical lymph nodes. The diagnostic approach includes thyroid-stimulating hormone, ultrasonography, and biopsy. Treatment options are surgical removal of the thyroid gland, with the addition of radioactive iodine therapy and systemic therapy, depending on the type and extent of the thyroid malignancy.
Thyrotoxicosis refers to the classic physiologic manifestations of excess thyroid hormones and is not synonymous with hyperthyroidism, which is caused by sustained overproduction and release of T3 and/or T4. Graves’ disease is the most common cause of primary hyperthyroidism, followed by toxic multinodular goiter and toxic adenoma. Subacute thyroiditis is an example of thyrotoxicosis without hyperthyroidism, and a pituitary adenoma, which secretes thyroid-stimulating hormone (TSH) is an example of secondary hyperthyroidism. Clinical features of thyrotoxicosis are mostly due to an increase in the metabolic rate and overactivity of the sympathetic nervous system (i.e., an increase in the β-adrenergic “tone”). Thyrotoxicosis is diagnosed by measuring the levels of TSH produced by the anterior pituitary gland and unbound T4 and T3. Depending on the etiology and clinical presentation, it may be treated pharmacologically, surgically, or with radioiodine.
Acute bronchitis is an infection of the mucous membrane of the bronchi without evidence of pneumonia. Due to its pathogenesis, acute bronchitis is frequently accompanied by an upper respiratory tract infection. Cases in which the trachea is also involved are referred to as tracheobronchitis. Acute bronchitis is usually viral (approximately 95% of all cases), and bacterial infections are usually caused by atypical bacteria. Acute bronchitis is diagnosed clinically, although a chest X-ray may be useful in ruling out pneumonia. Management is supportive, and antibiotics are not indicated in otherwise healthy adults.
Multiple endocrine neoplasia syndromes are autosomal dominant inherited conditions characterized by 2 or more hormone-producing tumors involving the endocrine organs. There are different types of MEN, namely MEN1–4. The MEN1 syndrome is associated with MEN1 gene mutation and has a predilection for primary hyperparathyroidism, pituitary adenomas, and pancreatic tumors (the 3 P’s). Due to the RET proto-oncogene mutation, MEN2 syndrome can be further categorized as MEN2A and MEN2B. Medullary thyroid carcinoma and pheochromocytoma are common features. The MEN2A variant is associated with primary hyperparathyroidism, whereas MEN2B (also considered MEN3) is associated with neuromas and Marfanoid habitus. The newer and rare entity, MEN4, has features of MEN1 but results from CDKN1B mutations. The diagnosis is clinical, and tumors are detected based on imaging and correlating hormone levels. Genetic testing plays a crucial role in MEN2 syndromes in determining further management. Treatment is dependent on the tumors that are present and genetic mutation.
Hypoparathyroidism is defined as reduced parathyroid hormone (PTH) levels due to poor function of the parathyroid glands. The cause of hypoparathyroidism is most commonly iatrogenic following neck surgery, but it can also be associated with genetic or autoimmune disorders as well as infiltrative diseases causing destruction of the normal parathyroid tissue. Deficiency of PTH results in hypocalcemia, which leads to increased neuromuscular excitability and osteosclerosis, as well as cardiac and neuropsychiatric manifestations. Treatment is based on calcium and vitamin D supplementation.
Atopic dermatitis, also known as eczema, is a chronic, relapsing, pruritic, inflammatory skin disease that occurs more frequently in children, although adults can also be affected. The condition is often associated with elevated serum levels of IgE and a personal or family history of atopy. Skin dryness, erythema, oozing, crusting, and lichenification are present. Pruritus is a cardinal symptom. Diagnosis is established clinically. The mainstays of management are avoidance of triggers, emollients, and topical corticosteroids.
Ulcerative colitis (UC) is an idiopathic inflammatory condition that involves the mucosal surface of the colon. It is a type of inflammatory bowel disease (IBD), along with Crohn's disease (CD). The rectum is always involved, and inflammation may extend proximally through the colon. Ulcerative colitis causes diffuse friability, erosions with bleeding, and loss of haustra, which are visible on endoscopy. Patients typically present with bloody diarrhea, colicky abdominal pain, tenesmus, and fecal urgency. Diagnosis is established via endoscopy with biopsy and by ruling out other causes of bloody diarrhea. Management is primarily through topical mesalamine, 6-mercaptopurine, or colectomy for severe cases. Complications include fulminant colitis, toxic megacolon, intestinal perforation, and increased risk of colorectal cancer.
Urticaria is raised, well-circumscribed areas (wheals) of edema (swelling) and erythema (redness) involving the dermis and epidermis with associated pruritus (itch). Urticaria is not a single disease but rather is a reaction pattern representing cutaneous mast cell degranulation resulting in the release of histamine and other vasoactive substances from mast cells and basophils in the dermis resulting in extravasation of plasma into the dermis. Urticaria can be caused by myriad inciting events, such as allergic reactions, infections, exposure, and many others. The diagnosis is made clinically. H1-antagonists are used as 1st-line treatment.
Hypertrophic cardiomyopathy (HCM) is the most commonly inherited cardiomyopathy, which is characterized by an asymmetric increase in thickness (hypertrophy) of the left ventricular wall, diastolic dysfunction, and often left ventricular outflow tract obstruction. Hypertrophic cardiomyopathy is caused by various gene mutations affecting the contractile components of the heart, known as sarcomeres. Inheritance of HCM is typically autosomal dominant, although sporadic mutations also occur. Patients may be asymptomatic, present with dyspnea and chest pain or suffer sudden cardiac death without prior symptoms. Diagnosis is made based on ECG, echocardiography, stress test, and cardiac MRI. Symptomatic HCM is typically treated with beta-blockers as the 1st-line therapy. Additional management depends on the presence of left ventricular outflow tract obstruction.
Cardiac arrest is the sudden, complete cessation of cardiac output with hemodynamic collapse. Patients present as pulseless, unresponsive, and apneic. Rhythms associated with cardiac arrest are ventricular fibrillation/tachycardia, asystole, or pulseless electrical activity. The treatment of cardiac arrest begins with basic life support (BLS) when out-of-hospital and advanced cardiac life support (ACLS) when in-hospital. Basic life support comprises checking the patient’s mental status, activating the emergency response system, and cardiopulmonary resuscitation (CPR). An automated external defibrillator (AED) should be used once available. High-quality CPR (with early defibrillation in shockable rhythms) is crucial to survival in cardiac arrest. Advanced cardiac life support includes CPR, securing the airway, administering medications (such as epinephrine), and identifying and treatment of the cause of cardiac arrest. Post-cardiac arrest care follows return of spontaneous circulation (ROSC).
Hypothyroidism is a condition characterized by a deficiency of thyroid hormones. Iodine deficiency is the most common cause worldwide, but Hashimoto's disease (autoimmune thyroiditis) is the leading cause in non–iodine-deficient regions. Primary hypothyroidism occurs with thyroid gland disorders, while the central type arises from pituitary and hypothalamic conditions. Thyroid hormones are integral in metabolic processes and in the development of the brain and other organs. Congenital hypothyroidism can result in significant mental disability due to the loss of thyroid hormones. The features of acquired hypothyroidism also reflect the effects of slowed organ function, such as fatigue, bradycardia, cold intolerance, and exertional dyspnea. Diagnosis is by thyroid function testing. Elevated thyroid stimulating hormone and low free thyroxine (T4) levels are noted. Treatment is with synthetic T4.
Endocarditis is an inflammatory disease involving the inner lining (endometrium) of the heart, most commonly affecting the cardiac valves. Both infectious and noninfectious etiologies lead to vegetations on the valve leaflets. Patients may present with nonspecific symptoms such as fever and fatigue. Important clinical exam findings include a new or changed heart murmur and common extra-cardiac signs, such as Osler nodes, Janeway lesions, splinter hemorrhages, and Roth spots. The diagnosis is based on clinical findings, blood cultures, and echocardiography showing valvular vegetations. Management includes intravenous antibiotics for infectious cases, addressing the underlying etiology for noninfectious cases, and surgical repair when necessary.
The shoulder complex comprises the glenohumeral joint, sternoclavicular joint, acromioclavicular joint, and the scapulothoracic articulation, and connects the upper limb to the trunk. This group of joints consists of the clavicle, scapula, and humerus bones, multiple muscles and supporting ligaments, cartilage, and bursae. The muscles ensure the mobility and stability of the shoulder and upper limb and are divided into 3 groups: anterior axioappendicular, posterior axioappendicular, and scapulohumeral muscles.
Condylomata acuminata are a clinical manifestation of genital HPV infection. Condylomata acuminata are described as raised, pearly, flesh-colored, papular, cauliflower-like lesions seen in the anogenital region that may cause itching, pain, or bleeding. Sexual contact is a common route of spread for HPV. While seen in all populations and ages, condylomata acuminata is most often seen in adolescence. HPV types 6 and 11 are responsible for 90% of warts and are considered low risk for malignancy; however, other types of HPV should be considered. Lesions rarely self-resolve; however, they can be removed via cryotherapy or topical antimitotic agents. While there is currently no treatment for HPV infection, it can be prevented through vaccination.
Primary amenorrhea is defined as the absence of menstruation in a girl by age 13 years in the absence of secondary sex characteristics or by the age of 15 years with the presence of secondary sex characteristics. Etiologies can originate in the hypothalamic–pituitary–ovarian (HPO) axis or from anatomic abnormalities in the uterus or vagina. Sometimes other endocrinopathies interfere with the sex hormones enough to suppress menstruation. Important factors to assess when working through the differential diagnosis are whether the patient has breast development (indicating exposure to estrogen from functional ovaries), the presence or absence of a uterus (indicating a potential genetic anomaly), and whether follicle-stimulating hormone (FSH) levels are high, low, or normal (providing insight into the HPO axis). Management includes correcting the underlying hormonal or anatomic issue, providing hormone replacement therapy (HRT), addressing fertility implications, and psychotherapy.
Pityriasis rosea is an acute, self-limited skin disease. The etiology is not known, and it commonly occurs in young adults. Patients initially present with a single, ovoid “herald patch.” This is followed by diffuse, pruritic, scaly, oval lesions over the trunk (often in a “Christmas tree” distribution on the back) and extremities. The diagnosis is clinical. Pityriasis rosea is a self-limiting condition; therefore, usually no treatment is required. However, topical steroids and antihistamines may be used for pruritus, if needed.
Septic arthritis is an infection of the joint due to direct inoculation, contiguous extension, or hematogenous spread of infectious organisms into the joint space. This process causes an acute, inflammatory, monoarticular arthritis. A variety of organisms have been implicated, most commonly Staphylococcus aureus. Previously damaged joints (e.g., rheumatoid arthritis) are at the highest risk of infection. Patients present with a swollen, warm, and tender joint, most commonly involving the knee. Positive cultures from arthrocentesis are diagnostic, with antibiotic therapy tailored to the specific organism. Repeated joint aspiration, or surgical drainage, is required in some cases. If the joint space is infected with a prosthetic in place, debridement and prosthesis removal may also be required.
Donovanosis (also known as granuloma inguinale) is an STD caused by Klebsiella granulomatis and is mainly seen in tropical regions. The condition is characterized by chronic, progressive, ulcerating disease mostly affecting the genital region. The patient presents with painless nodular lesions that ulcerate, commonly with a "beefy-red" base. There is no associated inguinal lymphadenopathy. Diagnosis is via history, clinical findings, and tissue smear or biopsy showing Donovan bodies, which are intracellular inclusion bodies inside macrophages. Treatment is with a prolonged course of antibiotics until lesions are healed, with monitoring for recurrence.
Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Symptoms of gastroenteritis may also commonly occur in children. Influenza is usually a self-limiting condition, though viral or secondary bacterial pneumonia may complicate the disease. Management is generally supportive, although NA inhibitors can be helpful if initiated within 48 hours of infection. Prevention relies on the annual vaccination of the public and practicing good hygiene.
Haemophilus is a genus of Gram-negative coccobacilli, all of whose strains require at least 1 of 2 factors for growth (factor V [NAD] and factor X [heme]); therefore, it is most often isolated on chocolate agar, which can supply both factors. The most common pathogenic species is H. influenzae, which is transmitted through respiratory droplets and can cause epiglottitis, meningitis, otitis media, and pneumonia. H. ducreyi is transmitted through sexual contact and is the cause of chancroid, a type of genital ulcer.
Cushing's syndrome or hypercortisolism is a disorder characterized by features resulting from chronic exposure to excess glucocorticoids. Cushing's syndrome may be exogenous, due to chronic glucocorticoid intake, or endogenous, due to increased adrenal secretion of cortisol or adrenocorticotropic hormone (ACTH) production from the pituitary gland or ectopic sources. Exogenous or iatrogenic hypercortisolism is the most common cause. Typical clinical features of hypercortisolism include central obesity, thin and bruisable skin, abdominal striae, secondary hypertension, hyperglycemia, and proximal muscle weakness. The initial diagnostic approach is to establish hypercortisolism via urinary and salivary cortisol tests along with low-dose dexamethasone suppression test. Once the elevated cortisol levels are confirmed, the etiology is determined based on ACTH levels, confirmatory biochemical tests, and subsequent imaging studies. Treatment options depend on the cause, and include surgery and medical therapy.
Henoch-Schönlein purpura (HSP), also known as immunoglobulin A vasculitis, is an autoimmune small-vessel vasculitis that typically presents as a tetrad of abdominal pain, arthralgia, hematuria, and purpuric rash. The pathophysiology involves the deposition of IgA immune complexes in multiple vessels following a trigger (infection/environmental), and the symptoms depend on the tissues that are involved. The diagnosis is established clinically, but can be supported with laboratory studies and skin or kidney biopsy. Management is mostly supportive, but may involve steroids and immunosuppressants in more severe cases. Prognosis is usually excellent, but some patients may develop end-stage renal failure.
The hemophilias are a group of inherited, or sometimes acquired, disorders of secondary hemostasis due to deficiency of specific clotting factors. Hemophilia A is a deficiency of factor VIII, hemophilia B a deficiency of factor IX, and hemophilia C a deficiency of factor XI. Patients present with bleeding events that may be spontaneous or associated with minor or major trauma. Management is focused mainly on treatment of acute bleeding events and prevention of bleeding events via replacement of deficient factors.
Vitiligo is the most common depigmenting disorder and is caused by the destruction of melanocytes. The etiology is unknown; however, genetic and autoimmune factors may play a role. Patients present with hypo- or depigmented macules or patches which often occur on the face, hands, knees, and/or genitalia. The diagnosis is clinical. Management depends on the severity and can include sun protection, topical or oral steroids, topical calcineurin inhibitors, immunosuppressants, and phototherapy.
Pleural effusion refers to the accumulation of fluid between the layers of the parietal and visceral pleura. Common causes of this condition include infection, malignancy, autoimmune disorders, or volume overload. Clinical manifestations include chest pain, cough, and dyspnea. Imaging can confirm the presence of a pleural effusion, and pleural fluid analysis can help in the evaluation of an etiology. Management is dependent on the underlying condition and whether the effusion is causing respiratory distress. Drainage of the effusion may provide symptomatic relief.
Hypersensitivity pneumonitis (HP), previously called extrinsic allergic alveolitis, is an immunologically induced inflammatory disease affecting the alveoli, bronchioles, and lung parenchyma. It is caused by repeated inhalation of an inciting agent in a susceptible host that triggers first a type III (complement-mediated) hypersensitivity reaction in the acute phase and then a type IV (delayed) reaction in the subacute and chronic phases. The clinical presentation of acute HP includes cough, fever, and malaise, while subacute and chronic forms present as insidious onset of a cough and dyspnea over weeks to months. Diagnosis is aided by high-resolution CT scans and bronchoalveolar lavage. Management includes avoiding the inciting agent and administration of steroids in subacute and chronic cases. Early treatment has a good prognosis, but long-term exposure can cause permanent scarring and fibrosis.
Gonorrhea is a sexually transmitted infection (STI) caused by the gram-negative bacteria Neisseria gonorrhoeae (N. gonorrhoeae). Gonorrhea may be asymptomatic but commonly manifests as cervicitis or urethritis with less common presentations such as proctitis, conjunctivitis, or pharyngitis. Without antibiotic treatment, complications can occur. Complications for men may include epididymitis, prostatitis, balanitis, and periurethral abscess. Women may develop pelvic inflammatory disease, which can cause perihepatitis and fertility issues. Disseminated gonococcal infection is associated with fever, dermatitis, tenosynovitis, septic arthritis, and (rarely) endocarditis or meningitis. Gonorrhea diagnosis is made by microscopy, culture, or nucleic acid amplification tests. Management generally involves ceftriaxone, but treatment with doxycycline should be pursued if a coinfection with Chlamydia trachomatis (C. trachomatis) is not excluded.
Sarcoidosis is a multisystem inflammatory disease that causes noncaseating granulomas. The exact etiology is unknown. Sarcoidosis usually affects the lungs and thoracic lymph nodes, but it can also affect almost every system in the body, including the skin, heart, and eyes, most commonly. Acutely, sarcoidosis presents with lymphadenopathy, fever, malaise, joint pains, a panniculitis on the shins known as erythema nodosum, and occasionally cough and shortness of breath. Chronic pulmonary sarcoidosis presents with an insidious onset of dyspnea, cough, chest pain, and a variety of other symptoms depending on the organ systems involved. Diagnosis often requires a biopsy of the granulomas. Management includes observation, NSAIDs, glucocorticoids, and potentially one of several steroid-sparing agents. Acute sarcoidosis is usually self-limiting with an excellent prognosis, but chronic sarcoidosis can lead to severe pulmonary fibrosis.
Molluscum contagiosum is a viral infection limited to the epidermis and is common in children below 5 years of age. Lesions appear as grouped, flesh-colored, dome-shaped papules with central umbilication. Molluscum contagiosum is mild in immunocompetent patients and self resolves within months. Immunocompromised individuals present with extensive lesions and systemic disease, which require treatment. Molluscum contagiosum is highly transmissible; therefore, patient education is key in its management. Cryotherapy with liquid nitrogen is the 1st-line treatment.
Bullous pemphigoid and pemphigus vulgaris are two different blistering autoimmune diseases. In bullous pemphigoid, autoantibodies attack the hemidesmosomes, which connect epidermal keratinocytes to the basement membrane. This attack results in large, tense subepidermal blisters. In pemphigus vulgaris, autoantibodies attack the desmosomal proteins, which connect the keratinocytes to one another. This attack results in a more severe, potentially fatal condition with fragile, flaccid blisters, usually with significant mucosal involvement. Diagnosis is made with biopsy and IF staining to identify and localize the antibodies. Management involves immunosuppression with corticosteroids and other steroid-sparing immunomodulatory agents.
Angioedema is a localized, self-limited (but potentially life-threatening), nonpitting, asymmetrical edema occurring in the deep layers of the skin and mucosal tissue. The common underlying pathophysiology involves inflammatory mediators triggering significant vasodilation and increased capillary permeability. Clinically, angioedema presents with swelling around the eyes, lips, tongue, mouth, bowel wall, extremities, or genitalia. Angioedema may also compromise the airway. Urticaria will be present when the angioedema is mediated by mast cells, but not when it is due to increases in bradykinin. Diagnosis is usually clinical but additional testing may include skin/serum testing for specific antigens and C4 level assessment. Management depends on the underlying mechanism but may include treatment for anaphylaxis, removing any offending agents, antihistamines, glucocorticoids, and/or therapies that target bradykinin.
Syphilis is a bacterial infection caused by the spirochete Treponema pallidum pallidum (T. p. pallidum), which is usually spread through sexual contact. Syphilis has 4 clinical stages: primary, secondary, latent, and tertiary. Primary syphilis begins with a chancre, a painless ulcer on the genitals. Progression to secondary syphilis manifests as a generalized maculopapular rash, which includes the palms and soles. The development of tertiary syphilis can cause severe neurologic (neurosyphilis), cardiovascular, and/or gummatous disease. The diagnosis is through both treponemal and nontreponemal testing. Penicillin G is the antibiotic of choice. The duration of management varies based on the stage of the disease.
Alcoholic liver disease is a spectrum of disorders ranging from fatty liver to cirrhosis secondary to chronic alcohol abuse. Excessive and prolonged consumption of alcohol results in impairment of the lipolysis pathway, causing inflammatory changes within the hepatocytes. Patients typically present during the hepatitis stage with jaundice, fever, and abdominal pain. Diagnosis is based on a history of alcohol abuse and confirmed by laboratory derangement with an AST/ALT ratio > 2. Alcoholic liver disease carries a high mortality rate if patients present with severe hepatitis. Management aims at alcohol abstinence for reversal (at certain stages) and addressing contributing factors (such as viral infections or drugs) to minimize damage to the hepatocytes. Approximately 10% of patients regress with alcohol abstinence during the hepatitis stage. Cirrhosis is frequently irreversible.
Osteoporosis refers to a decrease in bone mass and density leading to an increased number of fractures. There are 2 forms of osteoporosis: primary, which is commonly postmenopausal or senile; and secondary, which is a manifestation of immobilization, underlying medical disorders, or long-term use of certain medications. Osteoporosis most often presents clinically with frequent fractures and loss of vertebral height. Diagnosis is established by measuring bone mineral density. Management includes lifestyle modifications, maintaining adequate levels of calcium and vitamin D, and the use of bisphosphonates.
Pheochromocytoma is a catecholamine-secreting tumor derived from chromaffin cells. The majority of tumors originate in the adrenal medulla, but they may also arise from sympathetic ganglia (also referred to as paraganglioma). Symptoms are associated with excessive catecholamine production and commonly include hypertension, tachycardia, headache, and sweating. Pheochromocytomas are frequently familial and associated with genetic syndromes. Approximately 90% of pheochromocytomas are benign and surgical resection is the only curative treatment. Prognosis is generally good for benign, sporadic tumors that have been completely resected. Familial forms are associated with higher recurrence rates and malignant potential.
Coarctation of the aorta is a narrowing of the aorta between the aortic arch and the iliac bifurcation commonly around the point of insertion of the ductus arteriosus. Coarctation of the aorta is typically congenital and the clinical presentation depends on the age of the patient. Neonates present with heart failure upon the closure of the ductus arteriosus, while children and adults present with hypoperfusion and/or hypertension. Classic findings on physical exam include radio-/brachio-femoral delay and decreased blood pressure in the lower limbs. Diagnosis is confirmed by echocardiogram. Patients should be surgically managed as early as possible to avoid complications of hypertension. Close follow-up is required as the risk of hypertension and re-coarctation remain.
Duchenne muscular dystrophy (DMD) is an X-linked recessive genetic disorder that is caused by a mutation in the DMD gene. The mutation leads to the production of abnormal dystrophin, resulting in muscle-fiber destruction and replacement with fatty or fibrous tissue. Affected individuals present with progressive proximal muscle weakness leading to the eventual loss of ambulation, as well as contractures, scoliosis, cardiomyopathy, and respiratory failure. A marked elevation in CK may be observed. Genetic testing is used to confirm the diagnosis. Management is supportive and aimed at slowing disease progression and complications. Duchenne muscular dystrophy is fatal with a life expectancy of about 20 years of age.
Erysipelas is a bacterial infection of the superficial layer of the skin extending to the skin's superficial lymphatic vessels. This infection presents as a raised, well-defined, tender, and bright red rash. Typically on the legs or face, but erysipelas can occur anywhere on the skin. This infection occurs when bacteria enter through the points of skin breakdown. The most common bacteria causing this infection is group A Streptococci (especially Streptococcus pyogenes). Diagnosis is based mostly on the history and physical exam. Management includes antibiotics.
Necrotizing fasciitis is a life-threatening infection that causes rapid destruction and necrosis of the fascia and subcutaneous tissues. Patients may present with significant pain out of proportion to the presenting symptoms and rapidly progressive erythema of the affected area. Most patients will also have systemic signs of infection, including fever, hypotension, altered mental status, and multisystem organ failure. The diagnosis is primarily clinical since patients can quickly progress to septic shock without source control. This type of infection is a surgical emergency and requires emergent surgical debridement, parenteral antibiotics, and close hemodynamic monitoring.
Cutaneous squamous cell carcinoma (cSCC) is caused by malignant proliferation of atypical keratinocytes. This condition is the 2nd most common skin malignancy and usually affects sun-exposed areas of fair-skinned patients. The cancer presents as a firm, erythematous, keratotic plaque or papule. Histopathologic examination should be done for all suspected cases, as many lesions, such as actinic keratosis, mimic the appearance of SCC. Surgical excision is the mainstay of treatment. Overall prognosis is excellent for completely excised lesions, but certain high-risk features may predispose to metastatic disease and poor outcomes.
Benign or nonacute scrotal masses are represented by hydroceles, varicoceles, and spermatoceles. Key components to evaluation are physical exam and scrotal ultrasound. Hydroceles represent extra fluid in the tunica vaginalis, leading to a swollen scrotum. Varicoceles have a dilatation of the pampiniform venous plexus, giving the “bag of worms” appearance on exam. Spermatoceles present as an epididymal cyst, commonly arising from the head of the epididymis. Hydroceles, varicoceles, and spermatoceles are usually asymptomatic and do not require treatment unless they are causing pain or other complications.
Rickets and osteomalacia are disorders of decreased bone mineralization. Rickets affects the cartilage of the epiphyseal growth plates in children, while osteomalacia affects the sites of bone turnover in children and adults. Although most cases of rickets and osteomalacia are due to vitamin D deficiency, other genetic and nutritional disorders as well as medications can cause these disorders. Rickets commonly presents with skeletal deformities and growth abnormalities, while osteomalacia can present with bone pain, difficulty with ambulation and pathologic fractures. Diagnosis is made based on a combination of clinical findings, laboratory tests and imaging. Treatment includes vitamin D, calcium, and phosphorus supplementation.
Systemic lupus erythematosus (SLE) is a chronic autoimmune, inflammatory condition that causes immune-complex deposition in organs, resulting in systemic manifestations. Women, particularly those of African American descent, are more commonly affected. The clinical presentation can vary greatly. Notable clinical features include malar rash, nondestructive arthritis, lupus nephritis, serositis, cytopenia, thromboembolic disease, seizures, and/or psychosis. Diagnosis is based on clinical criteria, and includes tests to determine ANAs, SLE-specific antibodies, and specific clinical findings. The goal of management is to control symptoms and prevent organ damage, using corticosteroids, hydroxychloroquine, and immunosuppressants.
Pelvic inflammatory disease (PID) is defined as a polymicrobial infection of the upper female reproductive system. The disease can affect the uterus, fallopian tubes, ovaries, and adjacent structures. Pelvic inflammatory disease is closely linked with sexually transmitted diseases, most commonly caused by Chlamydia trachomatis and Neisseria gonorrhoeae, as well as organisms associated with bacterial vaginosis, such as Gardnerella vaginalis. Common symptoms are lower abdominal pain, cervical discharge, and irregular vaginal bleeding. Complications of PID can include ectopic pregnancy, chronic pelvic pain, and infertility. Diagnosis is primarily clinical in addition to PCR testing of cervical specimens and sometimes imaging or laparoscopy. Due to its polymicrobial nature, PID treatment is with combination antibiotic regimens.
Lung cancer is the malignant transformation of lung tissue and the leading cause of cancer-related deaths. The majority of cases are associated with long-term smoking. The disease is generally classified histologically as either small cell lung cancer or non-small cell lung cancer. Molecular profiling of the cancer provides further distinction of the tumor's biological behavior, prognosis, and treatment options. Symptoms include cough, dyspnea, weight loss, and chest discomfort. Regional and metastatic spread cause additional symptoms and complications depending on the location and organ(s) affected. Related paraneoplastic syndromes include hypercalcemia, hyponatremia, Lambert-Eaton syndrome, Cushing's syndrome, polydermatomyositis, and dermatomyositis. Definitive diagnosis and staging are made by biopsy, genetic mutation with biomarker testing, and imaging. Management is guided by the cancer stage and associated molecular profile. Lung cancer carries an overall poor prognosis.
Pulmonary embolism (PE) is a potentially fatal condition that occurs as a result of intraluminal obstruction of the main pulmonary artery or its branches. The causative factors include thrombi, air, amniotic fluid, and fat. In PE, gas exchange is impaired due to the decreased return of deoxygenated blood to the lungs. Deep vein thrombosis (DVT) is diagnosed in > 50% of patients presenting with symptoms, in whom the lower-extremity deep-venous system is the most common source of thrombus. Some individuals are asymptomatic, but the most common presenting symptom is dyspnea. The symptoms can be acute or chronic, and diagnosis is usually based on radiographic findings. Initial management is supportive and focuses on restoring oxygenation and hemodynamic stability. Both medical (systemic anticoagulants) and interventional therapies (catheter-based approach, surgery) are used to reestablish vessel patency.
Hypopituitarism is a condition characterized by pituitary hormone deficiency. This condition primarily results from a disease of the pituitary gland, but it may arise from hypothalamic dysfunction. Pituitary tumors are one of the most common causes. The majority of cases affect the anterior pituitary lobe (adenohypophysis), which accounts for 80% of the gland. The hormones produced from this lobe are growth hormone, follicle-stimulating hormone, luteinizing hormone, thyroid-stimulating hormone (TSH), adrenocorticotropic hormone, and prolactin. When the posterior lobe (neurohypophysis) is also damaged, loss of antidiuretic hormone and oxytocin occurs. All of these hormones regulate the activities of different organs, and thus the effects of pituitary hypofunction are multisystemic. The diagnosis is made through a combination of clinical findings, hormone levels, provocation tests, and brain imaging. Treatment is hormone replacement and addressing the etiology.
Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Associated symptoms, including fever, nausea and vomiting, weight loss, and bloody stools are also important to elicit from the history. Most causes of acute diarrhea are infectious and do not require additional workup. Since diarrhea is usually a self-limited condition, management is generally supportive. However, chronic diarrhea can require laboratory studies, stool studies, imaging, or procedures to determine the cause. Management ultimately hinges on treating the underlying pathology, though symptomatic and empiric therapies may be utilized under the right circumstances.
Chronic venous disease is a spectrum of disorders characterized by venous dilation and/or abnormal vein function in the lower extremities resulting from venous hypertension. "Chronic venous insufficiency" refers to the more severe forms of chronic venous disease. Skin changes typically distinguish chronic venous insufficiency from milder forms of venous disease (like varicose veins) and include skin pigmentation, stasis dermatitis, lipodermatosclerosis, and eventually, the development of ulcers. Diagnosis is usually based on physical exam findings alone, although venous duplex ultrasonography can provide additional information about the etiology, location, and extent of disease. The mainstay of management is compression therapy. A variety of surgical options also exist, including ablation, sclerotherapy, and valve repair. Venous ulcers are common as the disease progresses and are often very difficult to treat.
Aplastic anemia (AA) is a rare, life-threatening condition characterized by pancytopenia and hypocellularity of the bone marrow (in the absence of any abnormal cells) reflecting damage to hematopoietic stem cells. Aplastic anemia can be acquired or inherited, however, most cases of AA are acquired and caused by autoimmune damage to hematopoietic stem cells. Specifically known acquired causes and associations of AAs include medications, chemicals, high doses of whole-body radiation, viral infections, immune diseases, and pregnancy. Inherited or constitutional syndromes associated with AA include Fanconi anemia, dyskeratosis congenita, and Down syndrome. Therapies include transfusion support, immunosuppression, and bone marrow transplantation.
Ventricular septal defects (VSDs) are congenital cardiac malformations that feature an abnormal communication between the right and left ventricles. Presenting both in isolation or as part of a more complex disease, VSD is the most common congenital heart defect. While the degree of severity depends on the size of the defect, VSDs are classified on the basis of the anatomical location of the defect. Patients may be asymptomatic with smaller defects, whereas larger defects can present with respiratory or heart failure during infancy or childhood. A common clinical sign is a holosystolic murmur audible at the left sternal border. Diagnosis, both pre- and post-natal, is confirmed by echocardiogram. The majority of small VSDs close spontaneously, but those that are larger and symptomatic require medical stabilization followed by surgical repair.
Testicular torsion is the sudden rotation of the testicle, specifically the spermatic cord, around its axis in the inguinal canal or below. The acute rotation results in compromised blood flow to and from the testicle, which puts the testicle at risk for necrosis. Quick diagnosis and intervention is key to saving the affected testicle. Emergent surgical exploration with subsequent orchidopexy is required. Ultrasound or manual detorsion should not delay definitive care.
Rheumatoid arthritis (RA) is a symmetric, inflammatory polyarthritis and chronic, progressive, autoimmune disorder. Presentation occurs most commonly in middle-aged women with joint swelling, pain, and morning stiffness (often in the hands). Systemic inflammation can lead to extraarticular manifestations such as rheumatoid nodules, interstitial lung disease, Felty syndrome, and pericarditis. Prolonged and severe disease can lead to irreversible joint deformities. Diagnosis is based on strong clinical suspicion and confirmed by the presence of rheumatoid factor (RF), anti-cyclic citrullinated peptide (anti-CCP) antibodies, and characteristic imaging. Management involves long-term disease-modifying antirheumatic drugs (DMARDs), biologic agents, and physical therapy. Glucocorticoids and nonsteroidal antiinflammatory drugs (NSAIDs) are the treatment of choice for acute exacerbation.
Melanoma is a malignant tumor arising from melanocytes, the melanin-producing cells of the epidermis. These tumors are most common in fair-skinned individuals with a history of excessive sun exposure and sunburns. Melanomas usually present as pigmented skin lesions, but they can occur on mucosal surfaces, such as in the eyes, anal canal, and genital regions. Common findings may include Asymmetry of the lesion, irregular Border, varying Color, > 6 mm Diameter, and Evolving features (ABCDE). Definitive diagnosis is established with biopsy. Treatment relies primarily on surgical excision. The prognosis is very good for early-stage lesions but quite dismal for metastatic disease. Of all the skin malignancies, melanoma generally carries the worst prognosis.
Ankylosing spondylitis (also known as Bechterew’s disease or Marie-Strümpell disease) is a seronegative spondyloarthropathy characterized by chronic and indolent inflammation of the axial skeleton. Severe disease can lead to fusion and rigidity of the spine. Ankylosing spondylitis is most often seen in young men and is strongly associated with HLA-B27. Patients will have progressive back pain (which improves with activity), morning stiffness, and decreased range of motion of the spine. Extra-articular manifestations include fatigue, enthesitis, anterior uveitis, restrictive lung disease, and inflammatory bowel disease. The diagnosis is based on the clinical history, physical exam, and imaging demonstrating sacroiliitis and bridging syndesmophytes. Most patients are managed with physical therapy and nonsteroidal anti-inflammatory drugs (NSAIDs). More severe cases may require tumor necrosis factor-alpha inhibitors or surgery.
Congenital adrenal hyperplasia (CAH) consists of a group of autosomal recessive disorders that cause a deficiency of an enzyme needed in cortisol, aldosterone, and androgen synthesis. The most common subform of CAH is 21-hydroxylase deficiency, followed by 11β-hydroxylase deficiency. Clinical manifestations depend on the specific enzyme affected. Notably, CAH is the most common cause of ambiguous genitalia in genotypic female individuals. All forms of CAH cause low levels of cortisol, high levels of adrenocorticotropic hormone (ACTH), and adrenal hyperplasia. Laboratory studies help confirm the diagnosis. Lifelong glucocorticoid replacement is needed, and surgical correction of ambiguous genitalia is often performed.
The ductus arteriosus (DA) is a fetal blood vessel connecting the left pulmonary artery to the aorta. The DA allows blood to bypass pulmonary circulation. After birth, the DA remains open for up to 72 hours and then constricts and involutes, becoming the ligamentum arteriosum. Failure of this process to occur results in patent ductus arteriosus (PDA), a condition that causes up to 10% of congenital heart defects. Patent ductus arteriosus is twice as common in girls (especially premature infants) and causes a continuous machinery-like murmur on clinical examination. Patent ductus arteriosus may be associated with other cardiac defects; an echocardiogram can confirm the diagnosis. Treatment aims at closure of the remnant structure either through pharmacological or surgical means.
Polycystic ovarian syndrome (PCOS) is the most common endocrine disorder of reproductive-age women, affecting nearly 5%‒10% of women in the age group. Characterized by hyperandrogenism, chronic anovulation leading to oligomenorrhea (or amenorrhea), and metabolic dysfunction, PCOS increases a woman’s risk for infertility, endometrial hyperplasia or carcinoma, and cardiovascular disease. The pathophysiology is incompletely understood but thought to have a multifactorial genetic basis causing altered pulsatile release of gonadotropin-releasing hormone (GnRH), as well as increases in luteinizing hormone (LH), androgens, estrogen, and insulin: The result is chronic anovulation and hirsutism, which define the condition. Diagnosis is one of exclusion; therefore, other causes of abnormal uterine bleeding and hirsutism must be ruled out. Management includes attempting to restore normal ovulation through weight loss, oral contraceptive pills (OCPs), and fertility assistance.
Lung cancer is the leading cause of cancer-related death in the United States, with 90% of cases being fatal. The vast majority of cases are associated with smoking, and thus smoking cessation is encouraged to reduce a patient’s lifetime risk. Annual screening with low-dose computed tomography is recommended for early detection in patients 50–80 years of age with a significant smoking history. This screening program has been shown to significantly reduce mortality.
Alopecia is the loss of hair in areas anywhere on the body where hair normally grows. Alopecia may be defined as scarring or non-scarring, localized or diffuse, congenital or acquired, reversible or permanent, or confined to the scalp or universal; however, alopecia is usually classified using the 1st 3 factors. The etiologies of alopecia are usually divided into disorders in which the hair follicle is abnormal or damaged and those in which the hair follicle is normal but the cycling of hair growth is abnormal. The most common presentations are androgenetic hair loss, alopecia areata, traction alopecia, tinea capitis, and telogen effluvium. Diagnosis is made through a positive medical history and physical exam findings. Treatment depends on the type and potential for regrowth.
Blunt chest trauma is a non-penetrating traumatic injury to the thoracic cavity. Thoracic traumatic injuries are classified according to the mechanism of injury as blunt or penetrating injuries. Different structures can be injured including the chest wall (ribs, sternum), lungs, heart, major blood vessels, and the esophagus. The extent and specific type of thoracic traumatic injury can be identified by a proper history and physical examination supported by adequate imaging studies. Management depends on the specific type of injury.
Endometriosis is a common disease in which patients have endometrial tissue implanted outside of the uterus. Endometrial implants can occur anywhere in the pelvis, including the ovaries, the broad and uterosacral ligaments, the pelvic peritoneum, and the urinary and gastrointestinal tracts. Implants outside of the abdominopelvic cavity are also possible, though uncommon. Endometriosis typically presents in a reproductive-aged female with pelvic pain that worsens around menstruation. Endometrial implants tend to be inflammatory, leading to cyclic, chronic pain; adhesions; and an increased risk of infertility. The diagnosis is usually made clinically, though definitive diagnosis requires laparoscopy. Lab work is rarely useful. Management involves suppression of endometrial growth with progestins, typically with oral contraceptive pills. In severe cases, surgery is helpful to confirm the diagnosis and treat any implants.
Human immunodeficiency virus (HIV) infection is a sexually transmitted or blood-borne infection that destroys CD4 T cells. Chronic HIV infection and depletion of CD4 cells eventually results in acquired immunodeficiency syndrome (AIDS), which can be diagnosed by the presence of certain opportunistic diseases called AIDS-defining conditions. These conditions include a wide spectrum of bacterial, viral, fungal, and parasitic infections as well as several malignancies and generalized conditions. These serious and life-threatening diseases are generally not seen in immunocompetent patients. Treatment of HIV is very important in managing these diseases, and the incidence of AIDS-defining conditions has declined with the use of antiretroviral therapy.
Human immunodeficiency virus (HIV), a single-stranded RNA virus belonging to the Retroviridae family, is the etiologic agent of acquired immunodeficiency syndrome (AIDS). The human immunodeficiency virus is a sexually transmitted or blood-borne infection that attacks CD4+ T lymphocyte cells, macrophages, and dendritic cells, leading to eventual immunodeficiency. The presentation is marked by constitutional symptoms such as lymphadenopathy and fever. Further progression predisposes to opportunistic infections and malignancies. Diagnosis is by enzyme immunoassay for HIV-1 and -2. Additional tests include HIV viral load, genotyping, and CD4+ T lymphocyte count to determine therapy and evaluate treatment response and disease progression. Immediate treatment with combination antiretroviral therapy is recommended.
Aortic dissection occurs due to shearing stress from pulsatile pressure causing a tear in the tunica intima of the aortic wall. This tear allows blood to flow into the media, creating a “false lumen.” Aortic dissection is most commonly caused by uncontrolled hypertension. Complications arise due to partial occlusion of vital branches off the aorta and reduced blood flow to the brain, visceral organs, and extremities. Patients often present with acute, tearing chest or back pain. Computed tomography is the diagnostic modality of choice. All type A dissections (ascending aorta) are a surgical emergency due to the risk of imminent rupture. Type B dissections (descending aorta) can be managed medically with impulse control using beta-blockers and calcium channel blockers. If there is evidence of malperfusion to visceral organs or extremities, aneurysm dilation to > 5 cm, retrograde extension into the ascending aorta, or intractable pain, the patient will need evaluation for endovascular or open repair.
Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis complex bacteria. The bacteria usually attack the lungs but can also damage other parts of the body. Approximately 30% of people around the world are infected with this pathogen, with the majority harboring a latent infection. Tuberculosis spreads through the air when a person with active pulmonary infection coughs or sneezes. M. tuberculosis are acid-fast, slowly growing bacteria that can survive in macrophages, allowing for a latent infection that can remain asymptomatic for decades, posing a challenge to diagnosis, therapy, and prevention. The diagnosis is established with tuberculin skin test, sputum culture, and lung imaging. The mainstay of management is anti-mycobacterial drugs.
Sjögren syndrome (SS) is an autoimmune, inflammatory condition where glandular tissues, such as the salivary and lacrimal glands, are infiltrated by lymphocytes, resulting in decreased tear and saliva production. The disease mainly affects middle-aged women, and is associated with other autoimmune conditions. Patients may experience symptoms and complications related to dry eyes and mouth. There is a wide range of extraglandular manifestations, including Raynaud's phenomenon, neuropathy, and cutaneous vasculitis. Patients are also at an increased risk of developing non-Hodgkin's lymphoma. Diagnosis is based on the presence of symptoms, and is validated by the clinical examination, serologic studies, or salivary gland biopsy. A multidisciplinary approach is needed to manage patients and targets symptomatic relief, with immunosuppressive therapy reserved for severe symptoms.
Osteoarthritis (OA) is the most common form of arthritis, and is due to cartilage destruction and changes of the subchondral bone. The risk of developing this disorder increases with age, obesity, and repetitive joint use or trauma. Patients develop gradual joint pain, stiffness lasting < 30 minutes, and decreased range of motion. Physical exam may reveal crepitus with joint motion and osteophyte formation (Heberden's and Bouchard's nodes). The diagnosis is clinical and supported with radiographic joint findings. Management includes conservative measures, analgesic medications, glucocorticoid intra-articular injections, and surgery for advanced disease.
Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a disorder of impaired water excretion due to the inability to suppress the secretion of antidiuretic hormone (ADH). The inappropriate secretion of ADH can be due to various causes, including increased production by the pituitary gland due to trauma, disease, or certain medications; the ectopic secretion of ADH by cancer; or hereditary causes (nephrogenic SIADH). Syndrome of inappropriate antidiuretic hormone secretion is characterized by impaired water excretion leading to dilutional hyponatremia, which is mainly asymptomatic but may cause neurologic symptoms. Syndrome of inappropriate antidiuretic hormone secretion should be suspected in any patient with hyponatremia, hypo-osmolality, and high urine osmolality.
Abdominal injuries are classified according to their mechanism of injury as blunt or penetrating. In blunt abdominal trauma, the bowel, spleen, liver, kidneys, and pelvic organs can be injured. The extent and specific type of abdominal traumatic injury can be identified by a proper history and physical examination and confirmed by appropriate imaging studies. Management depends on the patient’s stability and specific type of injury.
Head trauma occurs when external forces are directed to the skull and brain structures, resulting in damage to the skull, brain, and intracranial structures. Head injuries can be classified as open (penetrating) or closed (blunt), and primary (from the initial trauma) or secondary (indirect brain injury), and range from mild to severe and life-threatening. The majority of cases are mild, but presentation can vary from a mild concussion to a comatose state depending on the severity of the insult. Management ranges from observation to intensive care monitoring and neurosurgical interventions. Prognosis is good for mild injuries, but severe trauma can result in death or permanent damage.
Paget's disease of bone (PDB), also known historically as osteitis deformans, is a focal disorder of bone metabolism that affects about 2%–9% of people. Commonly affected areas include the skull, spine, pelvis, and long bones of the lower extremity. The 2 main clinical manifestations of Paget's disease are bone pain and the consequences of bone deformities, such as fractures, osteoarthritis, or nerve impingement. The management includes bisphosphonates, calcitonin, and surgery for the management of fractures, deformities, and complications. The prognosis for PDB is good, especially if treatment is started before major changes have occurred in the bones.
Colorectal cancer (CRC) is the 2nd leading cause of cancer-related deaths in the United States. Colorectal cancer is a heterogeneous disease that arises from genetic and epigenetic abnormalities, with influence from environmental factors. Almost all cases of CRC are adenocarcinoma, and the majority of lesions come from the malignant transformation of an adenomatous polyp. Since most CRC cases are asymptomatic, screening colonoscopy or stool tests are generally recommended in patients ≥ 50 years of age. Along with screening, diagnosis is reached by colonoscopy, which allows visualization as well as tissue sampling. Treatment is primarily surgical, with chemotherapy reserved for advanced disease.
Barrett’s esophagus is a chronic gastroesophageal reflux disease (GERD) that leads to the replacement of stratified squamous epithelium with gastric columnar epithelium in the esophagus. The condition is associated with an increased risk of esophageal adenocarcinoma. Workup includes an esophagogastroduodenoscopy (EGD) showing proximal displacement of the squamocolumnar junction (Z-line) from the gastroesophageal junction (GEJ). Biopsies will confirm the diagnosis by revealing columnar epithelium and goblet cells in the distal esophagus. Treatment is primarily with proton pump inhibitors (PPIs) and lifestyle modifications. Surveillance with repeated EGD and biopsy is necessary to monitor for early signs of dysplasia.
Gastroesophageal reflux disease (GERD) occurs when the stomach acid frequently flows back into the esophagus. This backwash (acid reflux) can irritate the lining of the esophagus, causing symptoms such as retrosternal burning pain (heartburn). This condition may eventually lead to inflammation (esophagitis), metaplasia (Barrett’s esophagus), and progression to esophageal cancer. Uncomplicated GERD can be managed with lifestyle changes and over-the-counter medications. Sometimes, however, stronger medications or surgery may be required to ease symptoms and prevent complications.
A pneumothorax is a life-threatening condition in which air collects in the pleural space, causing partial or full collapse of the lung. A pneumothorax can be traumatic or spontaneous. Patients present with a sudden onset of sharp chest pain, dyspnea, and diminished breath sounds on exam. Symptom severity depends on the degree of the collapsed lung. A large or tension pneumothorax can result in cardiopulmonary collapse. A diagnosis is made with imaging, though tension pneumothorax is a clinical diagnosis. Management is based on the size and stability of the patient, and can include needle decompression and chest tube (thoracostomy) placement.
Esophagitis is the inflammation or irritation of the esophagus. The major types of esophagitis are medication-induced, infectious, eosinophilic, corrosive, and acid reflux. Patients typically present with odynophagia, dysphagia, and retrosternal chest pain. Diagnosis is by endoscopy and biopsy. Laboratory tests and imaging are obtained, depending on the degree of damage and involvement of other organ systems. Treatment for esophagitis depends on the underlying etiology and includes dietary changes, avoidance of offending agents, antibiotic therapy, or proton pump inhibitor use. In severe cases such as in corrosive injury, surgery may need to be performed. If left untreated, esophagitis can lead to complications such as strictures, metaplasia of the esophagus, and development of malignancy.
Hyperprolactinemia is defined as a condition of elevated levels of prolactin (PRL) hormone in the blood. The PRL hormone is secreted by the anterior pituitary gland and is responsible for breast development and lactation. Many factors contribute to the development of hyperprolactinemia. The most common cause is PRL-secreting pituitary adenomas (prolactinomas). Diagnosis is achieved through hormonal testing to rule out other endocrine conditions and confirmatory imaging tests. Dopamine agonists are the 1st-line drugs for treatment. Refractory cases require surgery and possibly radiation therapy.
Lyme disease is a tick-borne infection caused by the gram-negative spirochete Borrelia burgdorferi. Lyme disease is transmitted by the black-legged Ixodes tick (commonly known as a deer tick), which is only found in specific geographic regions. Patient presentation can vary depending on the stage of the disease and may include a characteristic erythema migrans rash. Neurologic, cardiac, ocular, and joint manifestations are also common in later stages. Diagnosis relies on clinical findings and tick exposure, and is supported by serological testing. Antibiotics are used for treatment. Avoidance of tick exposure is key to prevention in endemic areas.
Primary sclerosing cholangitis (PSC) is an inflammatory disease that causes fibrosis and strictures of the bile ducts. The exact etiology is unknown, but there is a strong association with inflammatory bowel disease (IBD). Patients typically present with an insidious onset of fatigue, pruritus, and jaundice, which can progress to cirrhosis and complications related to biliary obstruction. The diagnosis is established with magnetic resonance cholangiopancreatography (MRCP) or endoscopic retrograde cholangiopancreatography (ERCP). Liver transplantation is the only definitive treatment and is indicated in patients with advanced liver disease.
Diverticula are protrusions of the bowel wall occurring most commonly in the colon. The condition of having diverticula (called diverticulosis) is mostly asymptomatic. These diverticula can become symptomatic, however, when associated with diseases. Diverticulitis is the inflammation of diverticula, often presenting with lower abdominal pain and changes in bowel habits. The condition may be further complicated by abscess, perforation, fistula, and bowel obstruction. Management consists of antibiotics, fluid resuscitation, and bowel rest. Surgery is required for complications, failure of medical management, and recurrent disease. In most cases of diverticular bleeding, spontaneous cessation occurs. Invasive intervention will be needed for persistent or recurrent bleeding.
Peripheral artery disease (PAD) is obstruction of the arterial lumen resulting in decreased blood flow to the distal limbs. The disease can be a result of atherosclerosis or thrombosis. Patients may be asymptomatic or have progressive claudication, skin discoloration, ischemic ulcers, or gangrene. Onset may be insidious (atherosclerosis) or abrupt (thrombosis). Diagnosis is made with the clinical history, exam, and measurement of the ankle-brachial index. Imaging studies can determine the location and extent of the arterial disease. Treatment varies depending on the severity but can include lifestyle modifications, antiplatelet therapy, risk factor modifications, phosphodiesterase inhibitors, and revascularization.
Ectopic pregnancy refers to the implantation of a fertilized egg (embryo) outside the uterine cavity. The main cause is disruption of the normal anatomy of the fallopian tube. Consequently, affected patients may suffer from acute abdominal pain as the developing embryo increases in size. Ectopic pregnancy can be quickly diagnosed by means of an ultrasound and laboratory analysis. Management can be expectant, medical, or surgical. Severe cases involving rupture of the fallopian tube and hemorrhage are considered a medical emergency and require immediate surgery.
Appendicitis is the acute inflammation of the vermiform appendix and the most common abdominal surgical emergency globally. The condition has a lifetime risk of 8%. Characteristic features include periumbilical abdominal pain that migrates to the right lower quadrant, fever, anorexia, nausea, and vomiting. The diagnosis can frequently be established clinically, but imaging is used in uncertain cases. Computed tomography (CT) scan provides the highest diagnostic accuracy. Perforation occurs in 13%–20% of cases and can present as localized (abscess/phlegmon) or free perforation with generalized peritonitis. The standard treatment is appendectomy, but localized perforations are frequently managed non-operatively with antibiotics.
Drug-induced liver injury (DILI) is the most common cause of acute liver failure (ALF). Hepatotoxic drugs can cause injury to the hepatocytes directly in a predictable dose-dependent way or through idiosyncratic reactions (which may be mediated by immune or non-immune processes). The injury mechanisms can have the following effects: hepatitis, cholestasis, vascular lesions, or overlapping changes. The presentation can be acute or chronic, with severe toxicity manifesting as fulminant liver failure. The diagnosis of DILI requires a thorough history and laboratory tests including liver function tests (LFTs) and drug levels, if available. Management consists of discontinuing the drug, supportive therapy, and monitoring for complications. Acetaminophen, 1 of the most common causes of DILI, has a specific treatment, N-acetylcysteine (NAC).
Supraventricular tachycardias are related disorders in which the elevation in heart rate is driven by pathophysiology in the atria. This group falls under the larger umbrella of tachyarrhythmias and includes paroxysmal supraventricular tachycardias (PSVTs), ventricular pre-excitation syndromes (i.e. Wolff-Parkinson-White syndrome), atrial flutter, multifocal atrial tachycardia, and atrial fibrillation. Sinus tachycardia (> 100/min) is not a pathologic arrhythmia. The diagnosis of these conditions can be made using electrocardiogram (ECG), and treatment differs depending on the condition.
Pneumoconiosis is an occupational disease that results from the inhalation and deposition of mineral dusts and other inorganic particles in the lung. It can be categorized according to the type of causative particle involved or by the type of response provoked. Coal, silica, asbestos, and talc are the classic fibrogenic types, while beryllium provokes a granulomatous response, and cobalt is associated with giant cell pneumonia. Iron, tin, and barium are considered benign or inert particle types because they do not cause the same type of reactions as the others.
After exposure to the fibrogenic types of particles, macrophages and fibroblasts become activated within the pulmonary parenchyma leading to chronic inflammation and fibrosis, which can progress to respiratory failure and death. Occupational history and chest X-rays are the mainstays of diagnosis and staging. Management is mainly symptomatic.
Nevi (singular nevus), also known as “moles,” are benign neoplasms of the skin. Nevus is a non-specific medical term because it encompasses both congenital and acquired lesions, hyper- and hypopigmented lesions, and raised or flat lesions. Additionally, nevi can be found within different depths of the layers of the skin and originate from various types of cells (e.g., melanocytic, connective tissue, vascular). Nevi also have a wide variety of characteristic forms, which must be well understood in order to differentiate nevi from malignant melanoma. In this concept page, we will cover the basic classifications and most common types of nevi as well as the clinical criteria used to assess them.
Craniosynostosis is the premature fusion of 1 or more cranial sutures during the 1st year of life. Craniosynostosis is classified as simple or complex, and can be caused by environmental factors or genetic syndromes. Patients are typically asymptomatic and concern may arise from caregiver observations. Diagnosis is made clinically and by imaging of the head. Treatment is surgical and prognosis depends on classification and the presence of genetic syndromes.
Diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS) are serious, acute complications of diabetes mellitus. Diabetic ketoacidosis is characterized by hyperglycemia and ketoacidosis due to an absolute insulin deficiency. Hyperosmolar hyperglycemic state occurs due to a relative deficiency of insulin or insulin resistance, leading to severe hyperglycemia and elevated serum osmolality. Triggering factors include inadequate insulin therapy, underlying infection, concurrent medical illness, or drug side effects. Diabetic ketoacidosis patients tend to be younger, with type 1 diabetes, who present with acute symptoms, including abdominal pain, nausea, and vomiting. On the other hand, HHS patients are generally older, with type 2 diabetes, and will have gradual onset of symptoms, including altered mental status and neurologic changes. Both sets of patients will have polyuria, polydipsia, and evidence of severe dehydration. Diagnosis is based on laboratory values demonstrating hyperglycemia with ketoacidosis or hyperosmolality. Management involves aggressive fluid rehydration, insulin therapy, and correction of electrolyte abnormalities.
Asthma is a chronic inflammatory condition of the small airways of the lungs. The condition is characterized by airway hyperresponsiveness, variable airway obstruction, and airway inflammation. Manifestations include episodic wheezing, coughing, and shortness of breath. Management of asthma aims to reduce symptoms and minimize future risks and adverse outcomes (hospitalizations, loss of lung function, etc.). Medications commonly utilized include inhalers that allow bronchodilation and inflammatory control. Biologic agents are available for severe asthma.
Hereditary hemochromatosis (HH) is an autosomal recessive disorder most often associated with HFE gene mutations. Patients have increased iron intestinal absorption and iron deposition in several organs, such as the liver, heart, skin, and pancreas. The clinical presentation includes the triad of cirrhosis, diabetes, and skin bronzing. Other findings depend on the organ(s) involved. Diagnosis consists of iron studies, showing transferrin (Tf) and ferritin elevation. Genetic screening is recommended among family members. Imaging and invasive studies are performed depending on the associated complications. Management requires phlebotomy (or iron chelation therapy in some cases) to prevent disease progression. The prognosis is good for patients who are early in the disease and undergoing treatment. The presence of hepatic fibrosis is a poor prognostic factor.
Peptic ulcer disease (PUD) refers to the full-thickness ulcerations of duodenal or gastric mucosa. The ulcerations form when exposure to acid and digestive enzymes overcomes mucosal defense mechanisms. The most common etiologies include Helicobacter pylori (H. pylori) infection and prolonged use of non-steroidal anti-inflammatory drugs (NSAIDs). Patients may be asymptomatic or may present with abdominal pain, nausea, and early satiety. Peptic ulcer disease typically responds well to medical treatment consisting of H. pylori eradication, eliminating risk factors, and proton pump inhibitors (PPIs). If left untreated, it can lead to bleeding, perforation, gastric outlet obstruction, and gastric cancer.
Gastritis refers to inflammation of the gastric mucosa. Gastritis may occur suddenly (acute gastritis) or slowly over time (chronic gastritis). Gastritis may be asymptomatic or with symptoms, including burning abdominal pain (which either worsens or improves with eating), dyspepsia, nausea, and vomiting. The most common etiologies for gastritis are Helicobacter pylori infection and autoimmune disease. Chronic gastritis is a risk factor for gastric cancer. Management involves the use of proton pump inhibitors with antibiotics (in case of H. pylori infection), avoidance of offending agents, and replacement of associated deficiencies.
Mitral stenosis (MS) is the narrowing of the mitral valve (MV) orifice, leading to obstructed blood flow from the left atrium (LA) to the left ventricle (LV). Mitral stenosis is most commonly due to rheumatic heart disease. Mitral stenosis leads to impaired LV diastolic filling, increased LA pressure, and LA dilation, which can result in atrial fibrillation, pulmonary congestion, pulmonary hypertension, and right heart failure. Symptoms include exertional dyspnea, orthopnea, palpitations, fatigue, and hoarseness. Physical examination will demonstrate an opening snap, followed by a rumbling diastolic murmur. An echocardiogram is used for diagnosis. Treatment includes sodium restriction, diuretics, atrial fibrillation management, possible anticoagulation, and percutaneous commissurotomy or surgery.
Mitral regurgitation (MR) is the backflow of blood from the left ventricle (LV) to the left atrium (LA) during systole. Mitral regurgitation may be acute (myocardial infarction) or chronic (myxomatous degeneration). Acute and decompensated chronic MR can lead to pulmonary venous congestion, resulting in symptoms of dyspnea, orthopnea, and fatigue. Acute MR is an emergency because it can cause cardiogenic shock, and requires medical stabilization and surgery. In chronic severe MR, patients are evaluated for surgical repair or replacement.
Cholecystitis is the inflammation of the gallbladder (GB) usually caused by the obstruction of the cystic duct (acute cholecystitis). Mechanical irritation by gallstones can also produce chronic GB inflammation. Cholecystitis is one of the most common complications of cholelithiasis (calculous cholecystitis) but inflammation without gallstones (acalculous cholecystitis) can occur in a minority of patients. The acute type usually presents with right upper quadrant (RUQ) pain, fever, and leukocytosis. The diagnosis is made clinically and confirmed via ultrasound (US). The definitive management is cholecystectomy, preferred to be performed within 72 hours. This condition can present as a mild condition or as a severe disease (with complications such as gallbladder gangrene, perforation, empyema) which require emergent intervention.
Hemolytic uremic syndrome (HUS) is a clinical phenomenon most commonly seen in children that consists of a classic triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. Hemolytic uremic syndrome is a major cause of acute kidney injury in children and is most commonly associated with a prodrome of diarrheal illness caused by Shiga-like toxin-producing bacteria. Laboratory analysis confirms microangiopathic hemolytic anemia (hemoglobin < 8 g/dL, schistocytes, and negative direct Coombs), thrombocytopenia (platelet count < 140,000/mm³), and acute kidney injury (elevated creatinine and blood urea nitrogen (BUN)). The management of HUS is primarily through supportive care.
Cholelithiasis (gallstones) is the presence of stones in the gallbladder. Most gallstones are cholesterol stones, while the rest are composed of bilirubin (pigment stones) and other mixed components. Patients are commonly asymptomatic but may present with biliary colic (intermittent pain in the right upper quadrant). The diagnosis is established by ultrasound. Management options include supportive care to prevent and control associated symptoms. When indicated, cholecystectomy is the definitive treatment. Gallstones may lead to complications such as choledocholithiasis (a stone trapped in the common bile duct), cholecystitis (inflammation of the gallbladder), or cholangitis (biliary sepsis). These conditions require urgent medical attention.
Hepatic encephalopathy is a reversible condition in which elevated ammonia levels cause impaired brain function in patients with advanced liver disease. Hepatic encephalopathy can be precipitated by conditions that affect the normal absorption, metabolism, or clearance of ammonia, including dehydration, renal failure, infections, and gastrointestinal bleeding. Patients present with a progression of symptoms, from minimal confusion and asterixis to stupor and coma. Diagnosis is clinical and requires the exclusion of alternative diagnoses. Management involves addressing the causative factor and decreasing the systemic absorption of ammonia with lactulose or rifaximin.
Hepatorenal syndrome (HRS) is a potentially reversible cause of acute kidney injury that develops secondary to liver disease. The main cause of HRS is hypovolemia, often as a result of forced diuresis or drainage of ascites. This leads to renal vasoconstriction resulting in hypoperfusion of the kidneys. Patients typically present with edema, oliguria or anuria, and ascites in the setting of acute or chronic liver injury. Hepatorenal syndrome is considered a diagnosis of exclusion. Treatment is with agents that cause systemic vasoconstriction and, therefore, improve renal perfusion. This includes octreotide and midodrine. Most cases of hepatorenal syndrome have a poor prognosis.
The axilla is a pyramid-shaped space located between the upper thorax and the arm. The axilla has a base, an apex, and 4 walls (anterior, medial, lateral, posterior). The base of the pyramid is made up of the axillary skin. The apex is the axillary inlet, located between the 1st rib, superior border of the scapula, and clavicle. The apex houses various vessels and nerves, including the axillary artery and its branches, the axillary vein and its tributaries, the branches of the brachial plexus, and the axillary lymph nodes.
Irritable bowel syndrome (IBS) is a functional bowel disease characterized by chronic abdominal pain and altered bowel habits without an identifiable organic cause. The etiology and pathophysiology of this disease are not well understood, and there are many factors that may contribute. Irritable bowel syndrome is a diagnosis of exclusion, and organic causes should be ruled out. Once diagnosed, the emphasis is on education and reassurance. Dietary modifications and symptom-control measures may also be instituted.
Thromboangiitis obliterans (TAO), also known as Buerger’s disease, is a rare condition causing inflammatory thrombosis of the small- to medium-sized arteries and veins of the upper and lower extremities. Patients are typically young smokers presenting with distal extremity ischemia, ulcers, or gangrene. Superficial thrombophlebitis and Raynaud's phenomenon can be early manifestations. Diagnosis is based on clinical findings, vascular testing, and angiography. Other potential diagnoses must be ruled out. The use of tobacco products is strongly associated with the disease; therefore, smoking cessation is an essential part of management and decreases the risk of amputation.
Calcium channel blockers (CCBs) are a class of medications that inhibit voltage-dependent L-type calcium channels of cardiac and vascular smooth muscle cells. The inhibition of these channels produces vasodilation and myocardial depression. There are 2 major classes of CCBs: dihydropyridines and non-dihydropyridines, which differ in their selectivity for cardiac or vascular smooth muscle cells. Broadly, these agents are used to treat hypertension, angina, and tachyarrhythmias. Side effects are from vasodilation (headache, peripheral edema, reflex tachycardia) or a consequence of reduced myocardial contractility and nodal conduction velocity (bradycardia).
Gastrointestinal bleeding (GIB) is a symptom of multiple diseases within the gastrointestinal (GI) tract. Gastrointestinal bleeding is designated as upper or lower based on the etiology’s location to the ligament of Treitz. It is more common to have bleeding in the upper GI tract, with peptic ulcer disease being the most frequent cause. Depending on the location of the bleeding, the patient may present with hematemesis (vomiting blood), melena (black, tarry stool), or hematochezia (fresh blood in stools). Some patients presenting with GIB can be hemodynamically unstable and require emergent stabilization and evaluation. The source of the bleed can often be located and treated with endoscopy.
Celiac disease (also known as celiac sprue or gluten enteropathy) is an autoimmune reaction to gliadin, which is a component of gluten. Celiac disease is closely associated with HLA-DQ2 and HLA-DQ8. The immune response is localized to the proximal small intestine and causes the characteristic histologic findings of villous atrophy, crypt hyperplasia, and intraepithelial lymphocytosis. Patients typically present with diarrhea and symptoms related to malabsorption (steatorrhea, weight loss, and nutritional deficiencies). Patients are screened with serological antibody testing, and diagnosis is confirmed by small intestine biopsy. Treatment requires a lifelong gluten-free diet.
Atrial flutter is a regular supraventricular tachycardia characterized by an atrial heart rate between 240/min and 340/min (typically 300/min), atrioventricular (AV) node conduction block, and a “sawtooth” pattern on an electrocardiogram (ECG). There are many cardiac and non-cardiac causes, but patients will usually have underlying structural heart disease. Symptoms include palpitations, shortness of breath, chest pain, dizziness, and nausea. Management is similar to atrial fibrillation, with a focus on rhythm control and preventing systemic embolization.
Bradyarrhythmia is a rhythm in which the heart rate is less than 60/min. Bradyarrhythmia can be physiologic, without symptoms or hemodynamic change. Pathologic bradyarrhythmia results in reduced cardiac output and hemodynamic instability causing syncope, dizziness, or dyspnea. Bradyarrhythmia is due to dysfunction in the sinoatrial (SA) node, atrioventricular (AV) node, or the lower conduction system. Bradyarrhythmia can be associated with an intrinsic cardiac abnormality or with medications, electrolyte imbalances, and systemic diseases. Arrhythmia is detected by electrocardiogram (ECG). Additional tests such as event recorders are performed if symptoms are less frequent and require a longer observation period. There are bradyarrhythmias requiring no intervention. In symptomatic or life-threatening conduction abnormalities such as complete heart block, permanent pacemaker placement is the mainstay of treatment.
Aortic stenosis (AS), or the narrowing of the aortic valve aperture, is the most common valvular heart disease. While rheumatic heart disease remains the most frequent etiology worldwide, degenerative AS and congenital bicuspid valve defect are the 2 usual causes in developed countries. Aortic stenosis gradually progresses to heart failure, producing exertional dyspnea, angina, and/or syncope. A crescendo-decrescendo systolic murmur is audible in the right upper sternal border. Doppler echocardiography is the imaging of choice, showing structural and flow changes in the valvular area. Valve replacement is the only effective treatment for symptomatic severe AS. Indications for the procedure depend on the patient's symptoms, degree of AS severity, exercise tolerance, concurrent cardiac abnormalities, surgical risk, and life expectancy.
Gastric cancer is the 3rd-most common cause of cancer-related deaths worldwide. The majority of cases are from adenocarcinoma. The modifiable risk factors include Helicobacter pylori infection, smoking, and nitrate-rich diets. Hereditary syndromes, pernicious anemia, and prior partial gastrectomy are among the endogenous risk factors. When symptoms such as epigastric fullness, vomiting, and weight loss occur, it is likely that the cancer is in the advanced stage. Diagnosis is confirmed with esophagogastroduodenoscopy and biopsy. Imaging studies and laparoscopy aid in determining the cancer stage. Consequently, staging dictates the management approach. Management consists of gastrectomy and chemoradiotherapy. Most cases are diagnosed in late stages, indicating a generally poor prognosis.
Aortic regurgitation (AR) is a cardiac condition characterized by the backflow of blood from the aorta to the left ventricle during diastole. Aortic regurgitation is associated with an abnormal aortic valve and/or aortic root stemming from multiple causes, commonly rheumatic heart disease as well as congenital and degenerative valvular disorders. Acute valvular insufficiency, which rapidly progresses to cardiogenic shock, is an emergency requiring immediate aortic valve surgery. Chronic AR develops gradually, allowing the left ventricle to adapt to the increased stroke volume. Thus, echocardiogram shows left ventricular hypertrophy and dilation along with valvular abnormalities. Eventually, congestive heart failure occurs as the left ventricle is unable to handle the hemodynamic overload. Aortic valve replacement is the mainstay of treatment for AR with left ventricular dysfunction.
Asthma is a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. The disease is believed to result from the complex interaction of host and environmental factors that increase disease predisposition, with inflammation causing symptoms and structural changes. Patients typically present with wheezing, cough, and dyspnea. Diagnosis is confirmed with a pulmonary function test showing a reversible obstructive pattern. Treatment, based on symptom severity, includes bronchodilators and inhaled corticosteroids for control of inflammation. Biologic agents targeting inflammatory mediators have been developed for severe persistent asthma.
The forearm is the region of the upper limb between the elbow and the wrist. The term “forearm” is used in anatomy to distinguish this area from the arm, a term that is commonly used to describe the entire upper limb. The forearm consists of 2 long bones (the radius and the ulna), the interosseous membrane, and multiple arteries, nerves, and muscles. The muscles are grouped into 2 compartments: anterior and posterior. The function of these muscles is flexion and extension of the wrist and fingers, while also contributing to flexion of the elbow.
Hydrocephalus is a potentially life-threatening condition caused by the excess accumulation of cerebrospinal fluid (CSF) within the ventricular system. Hydrocephalus can be classified as communicating, which is caused by either impaired CSF absorption or excess CSF production; or non-communicating, which is caused by a structural blockage in CSF flow. The causes of hydrocephalus can be congenital or acquired. The clinical presentation is often nonspecific with symptoms including headache, behavioral changes, developmental delays, or nausea and vomiting. If the hydrocephalus is congenital or acquired at a young age, infants often present with macrocephaly. Diagnosis is confirmed with neuroimaging (ultrasound, computed tomography of the head, or magnetic resonance imaging) showing ventriculomegaly. Treatment is most commonly surgical with the placement of a CSF shunt.
Kawasaki disease (KD), also known as mucocutaneous lymph node syndrome or infantile polyarteritis, is a medium-sized necrotizing febrile vasculitis that affects children < 5 years of age. Multiple systems are involved but the most serious is the predilection of the coronary arteries. Management involves intravenous immunoglobulin and high-dose aspirin. Follow-up requires serial echocardiograms to monitor for coronary artery aneurysm.
Obstructive sleep apnea (OSA) is a disorder characterized by recurrent obstruction of the upper airway during sleep, causing hypoxia and fragmented sleep. Obstructive sleep apnea is due to a partial or complete collapse of the upper airway and is associated with snoring, restlessness, sleep interruption, and daytime somnolence. The diagnosis relies on medical history, and polysomnography can confirm the diagnosis. Management includes lifestyle changes, methods of positive airway pressure, and surgical intervention.
The arm is the region of the upper limb that extends from the shoulder to the elbow joint and connects inferiorly to the forearm through the cubital fossa. It is divided into 2 fascial compartments (anterior and posterior) and houses numerous structures, including the humerus; the brachial and profunda brachii arteries; the basilic, cephalic, and brachial veins; the radial, median, ulnar, and musculocutaneous nerves; and the flexor and extensor muscles of the arm.
Vaccination is the administration of a substance to induce the immune system to develop protection against a disease. Unlike passive immunization, which involves the administration of pre-performed antibodies, active immunization constitutes the administration of a vaccine to stimulate the body to produce its own antibodies. A vaccine is usually an antigenic, non-virulent form of a normally virulent microorganism. Vaccinations are a form of primary prevention and are the most effective form due to their safety, efficacy, low cost, and easy access. While the majority of vaccines are administered to young patients, some vaccines are targeted to diseases that occur in middle and old age, and are therefore administered to older patients.
Diabetes insipidus (DI) is a condition in which the kidneys are unable to concentrate urine. There are 2 subforms of DI: central DI (CDI) and nephrogenic DI (NDI). In CDI, the amount of antidiuretic hormone (ADH) produced by the hypothalamus or released from the pituitary gland is decreased. In nephrogenic DI, the kidneys fail to respond to circulating ADH. Both conditions result in the kidneys being unable to concentrate urine, leading to polyuria, nocturia, and polydipsia. Central and NDI are differentiated based on measured ADH levels and response to a water deprivation test. Central DI is treated with desmopressin, while nephrogenic DI is treated with diuretics and dietary salt restriction.
Raynaud's phenomenon refers to an abnormally marked and sudden vasoconstrictive response to cold temperature or emotional stress. The condition was first described by a medical student, Maurice Raynaud, in 1862. These "vasospastic attacks" are usually but not always limited to the fingers or toes and are associated with sharply demarcated triphasic color changes at the distal portions of the digits. There is initial blanching with numbness, followed by cyanosis, both of which correspond to the phase of constricted blood flow; subsequently, there is a red blush of reperfusion after rewarming or resolution of the provocative stressful event. Raynaud's phenomenon may be primary (idiopathic) or secondary.
Esophageal cancer is 1 of the most common causes of cancer-related deaths worldwide. Nearly all esophageal cancers are either adenocarcinoma (commonly affecting the distal esophagus) or squamous cell carcinoma (affecting the proximal two-thirds of the esophagus). Major risk factors for adenocarcinoma include smoking, obesity, and Barrett’s esophagus. For squamous cell carcinoma, risk factors include smoking, alcohol consumption, and certain dietary factors. Early-stage cancer is often asymptomatic, with dysphagia and weight loss presenting as the disease progresses. Diagnosis is by endoscopic biopsy or image-guided biopsy of the metastatic site. Management depends on the disease stage. Options include surgical resection, chemotherapy, and radiation. For unresectable esophageal cancers, palliative measures are provided for symptom relief and to prolong survival.
The elbow is the synovial hinge joint between the humerus in the upper arm and the radius and ulna in the forearm. The elbow consists of 3 joints, which form a functional unit enclosed within a single articular capsule. The elbow is the link between the powerful motions of the shoulder and the intricate fine-motor function of the hand. To provide that link, the motions of the elbow include extension and flexion as well as pronation and supination of the forearm.
Cystic fibrosis is an autosomal recessive disorder caused by mutations in the gene CFTR. The mutations lead to dysfunction of chloride channels, which results in hyperviscous mucus and the accumulation of secretions. Common presentations include chronic respiratory infections, failure to thrive, and pancreatic insufficiency. The gold standard for diagnosis is the sweat chloride test, which can be complemented by genetic testing. Cystic fibrosis ultimately leads to chronic inflammation and multisystem organ failure. Management includes CFTR modulator therapy and system-specific strategies for supportive care. Prognosis varies depending on treatment and complications. With optimal medical care, patients can live into their mid-40s.
Deep vein thrombosis (DVT) usually occurs in the deep veins of the lower extremities. The affected veins include the femoral, popliteal, iliofemoral, and pelvic veins. Proximal DVT is more likely to cause a pulmonary embolism (PE) and is generally considered more serious. Ultrasound can visualize the thrombus and anticoagulation is the primary mode of treatment; the main objective is the prevention of development of a PE.
Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. The most common symptoms include tachycardia, tachypnea, hypotension, altered mentation, and oliguria. Treatment measures vary depending on the suspected cause of shock and may include mechanical ventilation, IV crystalloids, vasopressors, and blood transfusion.
An aortic aneurysm is the abnormal dilation of a segment of the aorta. Abdominal aortic aneurysm is the most common aortic aneurysm, occurring frequently in the infrarenal area. Degenerative aortic disorders are the prevalent etiology, affecting patients > 60 years of age. Most aneurysms are asymptomatic, but can cause compression of surrounding structures or rupture, which is a life-threatening emergency. Diagnosis is often made by ultrasound. As aneurysmal rupture carries a high mortality rate, surveillance is recommended for asymptomatic cases to monitor aortic diameter. Elective surgery (the majority via endovascular aortic repair) is an effective way to reduce complications and aneurysm-related death. This surgery is performed based on aortic size, underlying condition, and associated symptoms.
Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy.
Achalasia is a primary esophageal motility disorder that develops from the degeneration of the myenteric plexus. This condition results in impaired lower esophageal sphincter relaxation and absence of normal esophageal peristalsis. Patients typically present with dysphagia to solids and liquids along with regurgitation. Diagnosis is established by high-resolution manometry. To rule out malignancy as a cause of achalasia, upper endoscopy is performed. Barium swallow study helps evaluate the esophageal morphology. Management options include pneumatic balloon dilation, surgical myotomy, and botulinum toxin injection. Choice of treatment is dependent on the type of achalasia and surgical risk. Medications are available for those who fail initial intervention; however, they provide the least benefit.
Gout is a heterogeneous metabolic disease associated with elevated serum uric acid levels (> 6.8 mg/dL) and abnormal deposits of monosodium urate in tissues. The condition is often familial and is initially characterized by painful, recurring, and usually monoarticular acute arthritis, or “gout flare,” followed later by chronic deforming arthritis. The kidneys can also be affected, and urate crystals can precipitate as chalkstone-like deposits (“tophi”) in the soft tissues, synovial tissues, or in bones near the joints. Hyperuricemia is due to overproduction and/or underexcretion of uric acid and is a necessary but insufficient precondition to developing urate crystal deposition disease (most hyperuricemic individuals never experience clinical gout). The most commonly involved joint is the first metatarsophalangeal joint. The identification of urate crystals in joint aspirate or tophi is diagnostic.
Effective therapies to relieve the pain of a gout flare include nonsteroidal anti-inflammatory drugs (NSAIDs), colchicine, and glucocorticoids; the choice of therapy depends on the individual and if there are any contraindications.
The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism (carbohydrates, proteins, lipids, hormones), nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. The liver can be divided into 4 lobes or 8 segments. Microscopically, it is divided into hepatic lobules. Its main neurovascular bundle is found within the transverse fissure of the liver, also called the porta hepatis.
Interstitial lung diseases are a heterogeneous group of disorders characterized by the inflammation and fibrosis of lung parenchyma, especially the pulmonary connective tissue in the alveolar walls. It may be idiopathic (e.g., idiopathic pulmonary fibrosis) or secondary to connective tissue diseases, medications, malignancies, occupational exposure, or allergens. Interstitial lung diseases commonly present with progressive exertional dyspnea and dry cough. Pulmonary function testing shows a restrictive lung disease pattern. Lung high-resolution computed tomography and biopsy usually establish the diagnosis. Treatment includes steroids and immunosuppressives.
Wilson disease (hepatolenticular degeneration) is an autosomal recessive disorder caused by various mutations in the ATP7B gene, which regulates copper transport within hepatocytes. Dysfunction of this transport mechanism leads to abnormal copper accumulations in the liver, brain, eyes, and other organs, with consequent major and variably expressed hepatic, neurologic, and psychiatric disturbances. Liver involvement may manifest as hepatitis, liver failure, or cirrhosis, while basal ganglia involvement causes the extrapyramidal signs. Most patients are diagnosed between the ages of 5 and 35 years (mean: 13 years). Diagnosis is established if the patient has low plasma ceruloplasmin, corneal deposits of copper (Kayser-Fleischer rings), and elevated copper levels in the urine. However, other tests are often needed since not all patients will have all these findings. The prognosis is good for patients without advanced liver disease and who are treated with the chelating agents penicillamine or trientine. Untreated Wilson disease is ultimately fatal, with patients dying from cirrhosis, acute liver failure, or complications due to progressive neurologic disease.
Impetigo is a highly contagious superficial bacterial infection typically caused by Staphylococcus aureus (most common) and Streptococcus pyogenes. Impetigo most commonly presents in children aged 2 to 5 years with lesions that evolve from papules to vesicles to pustules, which eventually break down to form characteristic “honey-colored” crusts. Infection can either be primary (bacterial infection of healthy, intact skin) or secondary (infection of pre-existing abrasions). The diagnosis is clinical, and management includes topical or systemic antibiotic therapy. Complications of impetigo include post-streptococcal glomerulonephritis, cellulitis, and scarlet fever.
Typhoid (or enteric) fever is a severe, systemic bacterial infection classically caused by the facultative intracellular and Gram-negative bacilli Salmonella enterica serotype Typhi (S. Typhimurium, formerly S. typhi). S. paratyphi serotypes A, B, or C can cause a similar syndrome. Up to 20 million new cases of typhoid fever occur each year worldwide, most commonly in undeveloped areas with poor sanitation. Transmission occurs through the fecal-oral route, and humans are the only known reservoir. Complications of typhoid fever include intestinal hemorrhage, pericarditis, visceral abscesses, and septicemia. Treatment is with fluoroquinolones. Prevention of typhoid fever is available through vaccination, hand hygiene, and safe food and water practices.
Erythema nodosum is an immune-mediated panniculitis (inflammation of the subcutaneous fat) caused by a type IV (delayed-type) hypersensitivity reaction. It commonly manifests in young women as tender, erythematous nodules on the shins. The underlying etiology varies and may be associated with infection, drug exposure, irritable bowel disease, pregnancy, or malignancy. The lesions often self-resolve within 8 weeks without scarring. Management focuses on identifying and treating the underlying cause.
Erythema multiforme (EM) is an acute hypersensitivity reaction characterized by targetoid skin lesions with multiple rings and dusky centers. Lesions may be accompanied by systemic symptoms (e.g., fever) and mucosal lesions (e.g., bullae). The majority of patients with EM have a history of recent viral (especially herpes simplex virus) or bacterial infection (usually Mycoplasma pneumoniae). Erythema multiforme is diagnosed clinically and treatment is directed toward the causative agent and alleviation of symptoms.
Pericarditis is an inflammation of the pericardium, often with fluid accumulation. It can be caused by infection (often viral), myocardial infarction, drugs, malignancies, metabolic disorders, autoimmune disorders, or trauma. Acute, subacute, and chronic forms exist. Acute pericarditis is usually idiopathic and manifests as fever, pleuritic chest pain, and an audible pericardial rub by auscultation. Diffuse upwardly concave ST-segment elevations in the initial ECG and pericardial effusion on echocardiography confirm the diagnosis. Acute pericarditis is usually self-limiting (2–6 weeks); therefore, management is conservative. If cardiac tamponade or constrictive pericarditis develops, cardiac output can be severely reduced. Treatment depends on the cause, but general measures include analgesics, anti-inflammatory drugs, colchicine, and rarely surgery.
Autoimmune hepatitis (AIH) is a rare form of chronic liver disease in which the immune system attacks the liver causing inflammation. It predominantly affects women. Clinical presentation ranges from asymptomatic cases to patients that present with symptoms of acute liver failure (jaundice, right upper quadrant pain). Because AIH has a 40% mortality in 6 months without treatment, early diagnosis and treatment are imperative. Diagnosis is established by detecting anti-smooth muscle antibodies and performing a confirmatory liver biopsy. Treatment includes corticosteroids and azathioprine. If treatment is initiated early in the disease course, the prognosis is favorable.
Transmissible spongiform encephalopathies are diseases caused by prions. Prions differ from viruses in that they are small, infectious pathogens that do not contain nucleic acid. Recognized spongiform encephalopathies include Creutzfeldt-Jakob Disease (CJD), variant Creutzfeldt-Jakob Disease (vCJD), Kuru, fatal familial insomnia (FFI), and Gerstmann-Straussler syndrome (GSS). Common characteristics of these diseases include dementia, ataxia, and myoclonus. Unfortunately, these diseases are associated with long incubation periods (20+ years) and once symptoms occur, rapidly progress to death.
Atrial fibrillation (AF or Afib) is a supraventricular tachyarrhythmia and the most common kind of arrhythmia. It is caused by rapid, uncontrolled atrial contractions and uncoordinated ventricular responses. There are many conditions that can cause AF, usually damage to the heart (e.g., coronary artery disease, previous myocardial infarction). Diagnosis is confirmed by an electrocardiogram that will show an “irregularly irregular” heartbeat with no distinct P waves and narrow QRS complexes. AF increases the risk of thromboembolic events. Treatment is primarily based on ventricular rate and rhythm control, which can be achieved through drugs and/or cardioversion. Anticoagulation is administered if the patient is at significant risk for thromboembolic events.
Gynecomastia is a benign proliferation of male breast glandular ductal tissue, usually bilateral, caused by increased estrogen activity, decreased testosterone activity, or medications. The condition is common and physiological in neonates, adolescent boys, and elderly men. Some cases are pathological or secondary to chronic liver disease, kidney disease, or hyperthyroidism. The majority of cases are asymptomatic and do not need treatment.
COVID-19, also known as Coronavirus disease, is a respiratory infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV 2). Transmission mainly occurs via direct contact or aerosol droplets. The disease may present asymptomatically or with fever and dry cough.
Antiplatelet agents are medications that inhibit platelet aggregation, a critical step in the formation of the initial platelet plug. Abnormal, or inappropriate, platelet aggregation is a key step in the pathophysiology of arterial ischemic events. The primary categories of antiplatelet agents include aspirin, ADP inhibitors, phosphodiesterase/adenosine uptake inhibitors, and glycoprotein IIb/IIIa inhibitors. Common indications for antiplatelet agents include the treatment and prevention of ischemic heart disease and stroke, peripheral artery disease, and other conditions associated with a high risk for arterial thrombosis.
Suicide is one of the leading causes of death worldwide. Patients with chronic medical conditions or psychiatric disorders are at increased risk of suicidal ideation, attempt, and/or completion. The patient assessment of suicide risk is very important as it may help to prevent a serious suicide attempt, which may result in death. Management of a suicidal patient includes medication, psychotherapy, and hospitalization to ensure patient safety.
Ultrasonography is an imaging technique used in medicine for the imaging of subcutaneous body structures, blood vessels, joints, and internal organs to exclude structural pathologies. This technique is based on the utilization of ultrasound (or high-frequency, inaudible sound waves). In medical imaging, the sound waves have a frequency of 2–18 megahertz (MHz). The equipment utilizes a transducer acting as the emitter and receptor of sound waves, and a central computer processes the electrical signals to generate the image. The general advantages of this type of imaging is its low cost, availability, and safety. Some specialties that rely heavily on ultrasound examination are cardiology, nephrology, general surgery, gastroenterology, emergency medicine, and obstetrics.
An insulinoma is a type of functional neuroendocrine tumor that manifests with hypoglycemia due to autologous secretion of insulin. It more commonly presents as a solitary benign tumor but can sometimes be associated with MEN type 1 (MEN1). Patients present with fasting hypoglycemia, which may manifest as episodes of diaphoresis, palpitations, tremor, and confusion. Insulinoma is usually diagnosed with high insulin, C peptide, and proinsulin levels despite the patient’s hypoglycemia. Localization of the insulinoma is done with imaging. Surgical removal of the insulinoma is the treatment of choice, but medical therapy may be utilized to prevent hypoglycemia in those who cannot undergo surgery.
Myelodysplastic syndromes (MDS) are a group of clonal neoplasms with maturation defects characterized by dysplasia, cytopenia, and immature bone marrow precursors. Myelodysplastic syndromes can be idiopathic, or secondary to various injurious exposures such as cytotoxic chemotherapy, ionizing radiation, or environmental toxins. The median patient age is 70 years old. Presentation includes symptoms of anemia (fatigue), neutropenia (infection), or thrombocytopenia (bleeding). The diagnosis is based on bone marrow evaluation, which reveals cytopenia, dysplasia in at least 1 lineage, and blast cells in < 20% of marrow cellularity. Cytogenetic and molecular studies are required for classification, prognosis, and therapy-related decisions. An increased cumulative risk of transformation to AML is present and varies depending on MDS subtype. Management includes supportive care, use of hematopoietic growth factors, immunosuppressive therapy, and allogeneic hematopoietic cell transplantation.
Tinea infections are a group of diseases caused by fungi infecting keratinized tissue (hair, nails, and skin). These infections are termed dermatomycoses and are caused by the dermatophyte fungi. There are approximately 40 dermatophyte fungi that are part of 3 genera, including Trichophyton, Epidermophyton, and Microsporum. These infections can affect any part of the body but occur most often in warm, moist regions like the groin and the feet. The diagnosis is clinical with characteristic skin findings, but it can be confirmed with microscopy of skin scrapings. The treatment depends on the site and magnitude of infection but typically begins with topical antifungals like the -azole drugs and terbinafine, and it may progress to oral versions of these medications if topical treatment fails.
Primary myelofibrosis (PMF) is a myeloproliferative neoplasm characterized by chronic myeloproliferation with nonclonal fibroblastic deposition, resulting in bone marrow fibrosis. The abnormality stems from genetic mutations of the hematopoietic stem cells (typically, JAK2 mutation). Primary symptoms are anemia and extramedullary hematopoiesis, which include severe fatigue, weight loss, and hepato