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Mononucleosis

Infectious mononucleosis (IM), also known as “the kissing disease,” is a highly contagious viral infection caused by the Epstein-Barr virus Epstein-Barr Virus Epstein-Barr virus (EBV) is a linear, double-stranded DNA virus belonging to the Herpesviridae family. This highly prevalent virus is mostly transmitted through contact with oropharyngeal secretions from an infected individual. The virus can infect epithelial cells and B lymphocytes, where it can undergo lytic replication or latency. Epstein-Barr Virus. Its common name is derived from its main method of transmission: the spread of infected saliva Saliva The clear, viscous fluid secreted by the salivary glands and mucous glands of the mouth. It contains mucins, water, organic salts, and ptyalin. Salivary Glands: Anatomy via kissing. Clinical manifestations of IM include fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, tonsillar pharyngitis Pharyngitis 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. Pharyngitis, and lymphadenopathy Lymphadenopathy Lymphadenopathy is lymph node enlargement (> 1 cm) and is benign and self-limited in most patients. Etiologies include malignancy, infection, and autoimmune disorders, as well as iatrogenic causes such as the use of certain medications. Generalized lymphadenopathy often indicates underlying systemic disease. Lymphadenopathy. Diagnosis is clinical and confirmed through heterophile antibody testing or specific serologic antibody testing. There is currently no specific antiviral Antiviral Antivirals for Hepatitis B therapy available for this condition.

Last updated: Sep 22, 2022

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Introduction

Definition

Infectious mononucleosis (IM) is a viral infectious disease caused by the Epstein-Barr virus Epstein-Barr Virus Epstein-Barr virus (EBV) is a linear, double-stranded DNA virus belonging to the Herpesviridae family. This highly prevalent virus is mostly transmitted through contact with oropharyngeal secretions from an infected individual. The virus can infect epithelial cells and B lymphocytes, where it can undergo lytic replication or latency. Epstein-Barr Virus ( EBV EBV Epstein-barr virus (EBV) is a linear, double-stranded DNA virus belonging to the herpesviridae family. This highly prevalent virus is mostly transmitted through contact with oropharyngeal secretions from an infected individual. The virus can infect epithelial cells and B lymphocytes, where it can undergo lytic replication or latency. Epstein-Barr Virus) and is characterized by a triad of fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, tonsillar pharyngitis Pharyngitis 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. Pharyngitis, and lymphadenopathy Lymphadenopathy Lymphadenopathy is lymph node enlargement (> 1 cm) and is benign and self-limited in most patients. Etiologies include malignancy, infection, and autoimmune disorders, as well as iatrogenic causes such as the use of certain medications. Generalized lymphadenopathy often indicates underlying systemic disease. Lymphadenopathy.  

Synonyms

  • Mononucleosis infectiosa
  • Pfeiffer’s disease or Pfeiffer‘s glandular fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever
  • “Mono” or “kissing disease”

Epidemiology

  • 90%–95% lifetime prevalence Prevalence The total number of cases of a given disease in a specified population at a designated time. It is differentiated from incidence, which refers to the number of new cases in the population at a given time. Measures of Disease Frequency worldwide
  • Occurs more frequently in spring and autumn
  • Children and adolescents aged 15–19 years are the most commonly affected 
  • A common cause of viral pharyngitis Pharyngitis 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. Pharyngitis, especially among young adults in the United States
  • Clinical infection is 30 times higher in Caucasians Caucasians Esophageal Cancer than African Americans in the United States

Etiology

EBV EBV Epstein-barr virus (EBV) is a linear, double-stranded DNA virus belonging to the herpesviridae family. This highly prevalent virus is mostly transmitted through contact with oropharyngeal secretions from an infected individual. The virus can infect epithelial cells and B lymphocytes, where it can undergo lytic replication or latency. Epstein-Barr Virus belongs to the group of human herpesviruses (HHV-4).

Pathophysiology

Pathogenicity

EBV EBV Epstein-barr virus (EBV) is a linear, double-stranded DNA virus belonging to the herpesviridae family. This highly prevalent virus is mostly transmitted through contact with oropharyngeal secretions from an infected individual. The virus can infect epithelial cells and B lymphocytes, where it can undergo lytic replication or latency. Epstein-Barr Virus has an exceptionally high species specificity:

  • Replicates almost exclusively in human epithelial cells of the oropharynx Oropharynx The middle portion of the pharynx that lies posterior to the mouth, inferior to the soft palate, and superior to the base of the tongue and epiglottis. It has a digestive function as food passes from the mouth into the oropharynx before entering esophagus. Pharynx: Anatomy and in B lymphocytes B lymphocytes Lymphoid cells concerned with humoral immunity. They are short-lived cells resembling bursa-derived lymphocytes of birds in their production of immunoglobulin upon appropriate stimulation. B cells: Types and Functions
  • Has not been recovered in the environment, suggesting that its major reservoir Reservoir Animate or inanimate sources which normally harbor disease-causing organisms and thus serve as potential sources of disease outbreaks. Reservoirs are distinguished from vectors (disease vectors) and carriers, which are agents of disease transmission rather than continuing sources of potential disease outbreaks. Humans may serve both as disease reservoirs and carriers. Escherichia coli is humans

Transmission

  • The disease is mainly transmitted via contact with body secretions, primarily oropharyngeal secretions
    • Smear infection (direct contact infection): especially common in children by parents, playmates, etc ETC The electron transport chain (ETC) sends electrons through a series of proteins, which generate an electrochemical proton gradient that produces energy in the form of adenosine triphosphate (ATP). Electron Transport Chain (ETC).
    • Indirect infection: by touching contaminated objects 
    • Contact infection: especially in adolescents by infected saliva Saliva The clear, viscous fluid secreted by the salivary glands and mucous glands of the mouth. It contains mucins, water, organic salts, and ptyalin. Salivary Glands: Anatomy during kissing and sharing beverages; kissing appears to be a more important route than coitus
    • Rarely spreads through blood transfusions Blood transfusions The introduction of whole blood or blood component directly into the bloodstream. Transfusion Products and organ transplantation Organ Transplantation Transplantation is a procedure that involves the removal of an organ or living tissue and placing it into a different part of the body or into a different person. Organ transplantations have become the therapeutic option of choice for many individuals with end-stage organ failure. Organ Transplantation due to the use of highly sensitive nucleic acid amplification Nucleic acid amplification Laboratory techniques that involve the in-vitro synthesis of many copies of DNA or RNA from one original template. Septic Arthritis testing (NAAT) of donor tissue
    • Vertical transmission Vertical transmission The transmission of infectious disease or pathogens from one generation to another. It includes transmission in utero or intrapartum by exposure to blood and secretions, and postpartum exposure via breastfeeding. Congenital TORCH Infections of EBV EBV Epstein-barr virus (EBV) is a linear, double-stranded DNA virus belonging to the herpesviridae family. This highly prevalent virus is mostly transmitted through contact with oropharyngeal secretions from an infected individual. The virus can infect epithelial cells and B lymphocytes, where it can undergo lytic replication or latency. Epstein-Barr Virus appears to be exceptional.
  • The virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology spreads throughout the body from the oropharynx Oropharynx The middle portion of the pharynx that lies posterior to the mouth, inferior to the soft palate, and superior to the base of the tongue and epiglottis. It has a digestive function as food passes from the mouth into the oropharynx before entering esophagus. Pharynx: Anatomy and infects CD21-positive epithelia in the nasopharynx Nasopharynx The top portion of the pharynx situated posterior to the nose and superior to the soft palate. The nasopharynx is the posterior extension of the nasal cavities and has a respiratory function. Pharynx: Anatomy and B lymphocytes B lymphocytes Lymphoid cells concerned with humoral immunity. They are short-lived cells resembling bursa-derived lymphocytes of birds in their production of immunoglobulin upon appropriate stimulation. B cells: Types and Functions, which infiltrate other lymphoid tissue throughout the lymphoreticular system of the entire body. 
  • There is an immortalization of B lymphocytes B lymphocytes Lymphoid cells concerned with humoral immunity. They are short-lived cells resembling bursa-derived lymphocytes of birds in their production of immunoglobulin upon appropriate stimulation. B cells: Types and Functions and a strong increase in EBV EBV Epstein-barr virus (EBV) is a linear, double-stranded DNA virus belonging to the herpesviridae family. This highly prevalent virus is mostly transmitted through contact with oropharyngeal secretions from an infected individual. The virus can infect epithelial cells and B lymphocytes, where it can undergo lytic replication or latency. Epstein-Barr Virus levels. 
  • In primary infection Primary infection Herpes Simplex Virus 1 and 2, only a small number of viral proteins Proteins Linear polypeptides that are synthesized on ribosomes and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of amino acids determines the shape the polypeptide will take, during protein folding, and the function of the protein. Energy Homeostasis are likely to be expressed. This results in a mild immune response and lack of clinical symptoms.
  • Oral shedding of EBV EBV Epstein-barr virus (EBV) is a linear, double-stranded DNA virus belonging to the herpesviridae family. This highly prevalent virus is mostly transmitted through contact with oropharyngeal secretions from an infected individual. The virus can infect epithelial cells and B lymphocytes, where it can undergo lytic replication or latency. Epstein-Barr Virus usually persists for six months after the onset of illness and can be intermittently shed for decades.
Ebv infection cycle

The Epstein-Barr virus Epstein-Barr Virus Epstein-Barr virus (EBV) is a linear, double-stranded DNA virus belonging to the Herpesviridae family. This highly prevalent virus is mostly transmitted through contact with oropharyngeal secretions from an infected individual. The virus can infect epithelial cells and B lymphocytes, where it can undergo lytic replication or latency. Epstein-Barr Virus can infect both B cells B cells Lymphoid cells concerned with humoral immunity. They are short-lived cells resembling bursa-derived lymphocytes of birds in their production of immunoglobulin upon appropriate stimulation. B cells: Types and Functions and oropharyngeal epithelial cells. EBV EBV Epstein-barr virus (EBV) is a linear, double-stranded DNA virus belonging to the herpesviridae family. This highly prevalent virus is mostly transmitted through contact with oropharyngeal secretions from an infected individual. The virus can infect epithelial cells and B lymphocytes, where it can undergo lytic replication or latency. Epstein-Barr Virus enters B cells B cells Lymphoid cells concerned with humoral immunity. They are short-lived cells resembling bursa-derived lymphocytes of birds in their production of immunoglobulin upon appropriate stimulation. B cells: Types and Functions by binding to the cellular receptor Receptor Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors CD21 CD21 Molecular sites on or in B-lymphocytes, follicular dendritic cells, lymphoid cells, and epithelial cells that recognize and combine with complement C3D. Human complement receptor 2 (CR2) serves as a receptor for both C3dg and the gp350/220 glycoprotein of Human Herpesvirus 4 and binds the monoclonal antibody OKB7, which blocks binding of both ligands to the receptor. Epstein-Barr Virus, allowing fusion of the viral envelope Envelope Bilayer lipid membrane acquired by viral particles during viral morphogenesis. Although the lipids of the viral envelope are host derived, various virus-encoded integral membrane proteins, i.e. Viral envelope proteins are incorporated there. Virology with the cell membrane Cell Membrane A cell membrane (also known as the plasma membrane or plasmalemma) is a biological membrane that separates the cell contents from the outside environment. A cell membrane is composed of a phospholipid bilayer and proteins that function to protect cellular DNA and mediate the exchange of ions and molecules. The Cell: Cell Membrane. The lytic cycle Cycle The type of signal that ends the inspiratory phase delivered by the ventilator Invasive Mechanical Ventilation results in the production of infectious virions in both B cells B cells Lymphoid cells concerned with humoral immunity. They are short-lived cells resembling bursa-derived lymphocytes of birds in their production of immunoglobulin upon appropriate stimulation. B cells: Types and Functions and oropharyngeal epithelial cells. In B cells B cells Lymphoid cells concerned with humoral immunity. They are short-lived cells resembling bursa-derived lymphocytes of birds in their production of immunoglobulin upon appropriate stimulation. B cells: Types and Functions, lytic replication normally only takes place after reactivation Reactivation Herpes Simplex Virus 1 and 2 from latency, whereas in oropharyngeal epithelial cells the lytic replication often directly follows viral entry. During lytic replication, viral DNA DNA A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine). DNA Types and Structure polymerase is responsible for synthesizing the viral genome Genome The complete genetic complement contained in the DNA of a set of chromosomes in a human. The length of the human genome is about 3 billion base pairs. Basic Terms of Genetics. This contrasts with latency, in which host-cell DNA DNA A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine). DNA Types and Structure polymerase copies the viral genome Genome The complete genetic complement contained in the DNA of a set of chromosomes in a human. The length of the human genome is about 3 billion base pairs. Basic Terms of Genetics. However, latency does not result in the production of virions, since only a portion of EBV EBV Epstein-barr virus (EBV) is a linear, double-stranded DNA virus belonging to the herpesviridae family. This highly prevalent virus is mostly transmitted through contact with oropharyngeal secretions from an infected individual. The virus can infect epithelial cells and B lymphocytes, where it can undergo lytic replication or latency. Epstein-Barr Virus‘s genes Genes A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. DNA Types and Structure are expressed.

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Clinical Presentation

  • Incubation Incubation The amount time between exposure to an infectious agent and becoming symptomatic. Rabies Virus period: 4–8 weeks
  • Prodromal stage: usually asymptomatic (especially in children < 10 years, of whom only 10% are symptomatic) but can include malaise Malaise Tick-borne Encephalitis Virus, headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess, and low-grade fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever
  • Symptoms present in adolescents and adults and last 2–4 weeks.

Classic triad of symptoms

  1. Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever
  2. Tonsillitis Tonsillitis Tonsillitis is inflammation of the pharynx or pharyngeal tonsils, and therefore is also called pharyngitis. An infectious etiology in the setting of tonsillitis is referred to as infectious pharyngitis, which is caused by viruses (most common), bacteria, or fungi. Tonsillitis (swollen and erythematous tonsils Tonsils Tonsillitis that may be covered in exudate Exudate Exudates are fluids, cells, or other cellular substances that are slowly discharged from blood vessels usually from inflamed tissues. Pleural Effusion)
  3. Cervical lymphadenopathy Lymphadenopathy Lymphadenopathy is lymph node enlargement (> 1 cm) and is benign and self-limited in most patients. Etiologies include malignancy, infection, and autoimmune disorders, as well as iatrogenic causes such as the use of certain medications. Generalized lymphadenopathy often indicates underlying systemic disease. Lymphadenopathy
    • Most common in the posterior cervical and posterior auricular chains

Additional symptoms

  • Headache 
  • General malaise to persistent and severe fatigue
  • Petechiae present at the junction between the hard and soft palates
  • Fetor ex-ore (“halitosis”): foul-smelling breath
  • Hepato-, spleno-, or hepatosplenomegaly Hepatosplenomegaly Cytomegalovirus
    • May present with abdominal pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways and/or jaundice Jaundice 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. Jaundice
  • Generalized lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs node swelling Swelling Inflammation (tender, firm, mobile nodes)
  • Maculopapular Maculopapular Dermatologic Examination rash Rash Rocky Mountain Spotted Fever (similar to measles Measles Measles (also known as rubeola) is caused by a single-stranded, linear, negative-sense RNA virus of the family Paramyxoviridae. It is highly contagious and spreads by respiratory droplets or direct-contact transmission from an infected person. Typically a disease of childhood, measles classically starts with cough, coryza, and conjunctivitis, followed by a maculopapular rash. Measles Virus, present in approximately 5% of cases)

Hoagland syndrome: the maximum manifestation of infectious mononucleosis

  • Impaired nasal breathing
  • Periorbital Periorbital Orbital and Preseptal Cellulitis edema Edema 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. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema
  • Swollen upper eyelids Eyelids Each of the upper and lower folds of skin which cover the eye when closed. Blepharitis
  • Symptoms of chronic mononucleosis

Neurologic syndromes: can occur 2–4 weeks after initial symptom onset

  • Guillain-Barré syndrome Guillain-Barré syndrome 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). Guillain-Barré Syndrome
  • Facial and other cranial nerve palsies Cranial Nerve Palsies Cranial nerve palsy is a congenital or acquired dysfunction of 1 or more cranial nerves that will, in turn, lead to focal neurologic abnormalities in movement or autonomic dysfunction of its territory. Head/neck trauma, mass effect, infectious processes, and ischemia/infarction are among the many etiologies for these dysfunctions. Diagnosis is initially clinical and supported by diagnostic aids. Management includes both symptomatic measures and interventions aimed at correcting the underlying cause. Cranial Nerve Palsies
  • Aseptic inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification, meninges Meninges 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. Meninges: Anatomy, and/or central and peripheral nerves Peripheral Nerves The nerves outside of the brain and spinal cord, including the autonomic, cranial, and spinal nerves. Peripheral nerves contain non-neuronal cells and connective tissue as well as axons. The connective tissue layers include, from the outside to the inside, the epineurium, the perineurium, and the endoneurium. Nervous System: Histology

Chronic mononucleosis: rare, due to persistent viral replication

  • Chronic or recurrent fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever
  • Fatigue Fatigue The state of weariness following a period of exertion, mental or physical, characterized by a decreased capacity for work and reduced efficiency to respond to stimuli. Fibromyalgia
  • Weight loss Weight loss Decrease in existing body weight. Bariatric Surgery
  • Lymphadenopathy Lymphadenopathy Lymphadenopathy is lymph node enlargement (> 1 cm) and is benign and self-limited in most patients. Etiologies include malignancy, infection, and autoimmune disorders, as well as iatrogenic causes such as the use of certain medications. Generalized lymphadenopathy often indicates underlying systemic disease. Lymphadenopathy
  • Cytopenia
  • Interstitial pneumonia Pneumonia 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. Pneumonia
  • Hepatitis
Infectious mononucleosis

Pharyngitis Pharyngitis 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. Pharyngitis demonstrating exudative tonsillitis Tonsillitis Tonsillitis is inflammation of the pharynx or pharyngeal tonsils, and therefore is also called pharyngitis. An infectious etiology in the setting of tonsillitis is referred to as infectious pharyngitis, which is caused by viruses (most common), bacteria, or fungi. Tonsillitis and an enlarged uvula Uvula A fleshy extension at the back of the soft palate that hangs above the opening of the throat. Peritonsillar Abscess in an adolescent patient 5 days after the onset of infectious mononucleosis

Image: “Infectious mononucleosis” by University of Minnesota Medical School, Minneapolis, MN, USA. License: CC BY 4.0

Diagnosis

Diagnosis is based on clinical symptoms noted above with confirmatory testing.

  • Laboratory:
    • Absolute and relative lymphocytic leukocytosis (> 4,500/ml and > 50% of leukocytes) with > 10% atypical large reactive CD8+ T cells (“atypical lymphocytes”)
    • Mild anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview and Types, neutropenia Neutropenia Neutrophils are an important component of the immune system and play a significant role in the eradication of infections. Low numbers of circulating neutrophils, referred to as neutropenia, predispose the body to recurrent infections or sepsis, though patients can also be asymptomatic. Neutropenia, and thrombocytopenia Thrombocytopenia 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. Thrombocytopenia
    • ↑ Blood sedimentation rate
    • ↑ C-reactive protein
    • Mild ↑ transaminases Transaminases A subclass of enzymes of the transferase class that catalyze the transfer of an amino group from a donor (generally an amino acid) to an acceptor (generally a 2-keto acid). Most of these enzymes are pyridoxyl phosphate proteins. Autoimmune Hepatitis, alkaline phosphatase Alkaline Phosphatase An enzyme that catalyzes the conversion of an orthophosphoric monoester and water to an alcohol and orthophosphate. Osteosarcoma, and total bilirubin Bilirubin A bile pigment that is a degradation product of heme. Heme Metabolism
  • Mononuclear spot, monospot, or heterophile antibody test:
    • Detects heterophile antibodies Antibodies Immunoglobulins (Igs), also known as antibodies, are glycoprotein molecules produced by plasma cells that act in immune responses by recognizing and binding particular antigens. The various Ig classes are IgG (the most abundant), IgM, IgE, IgD, and IgA, which differ in their biologic features, structure, target specificity, and distribution. Immunoglobulins: Types and Functions produced in response to EBV EBV Epstein-barr virus (EBV) is a linear, double-stranded DNA virus belonging to the herpesviridae family. This highly prevalent virus is mostly transmitted through contact with oropharyngeal secretions from an infected individual. The virus can infect epithelial cells and B lymphocytes, where it can undergo lytic replication or latency. Epstein-Barr Virus infection
    • Has a sensitivity of 85% and specificity of 100%
    • Further testing is not necessary if reactive
  • Serology Serology The study of serum, especially of antigen-antibody reactions in vitro. Yellow Fever Virus:
    • Detects antibodies Antibodies Immunoglobulins (Igs), also known as antibodies, are glycoprotein molecules produced by plasma cells that act in immune responses by recognizing and binding particular antigens. The various Ig classes are IgG (the most abundant), IgM, IgE, IgD, and IgA, which differ in their biologic features, structure, target specificity, and distribution. Immunoglobulins: Types and Functions against EBV EBV Epstein-barr virus (EBV) is a linear, double-stranded DNA virus belonging to the herpesviridae family. This highly prevalent virus is mostly transmitted through contact with oropharyngeal secretions from an infected individual. The virus can infect epithelial cells and B lymphocytes, where it can undergo lytic replication or latency. Epstein-Barr Virus 
    • Positive immunoglobulin G represents a past infection
    • Positive immunoglobulin M represents a current infection
  • Histopathology of lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs nodes:
    • The picture of polymorphic hyperplasia Hyperplasia An increase in the number of cells in a tissue or organ without tumor formation. It differs from hypertrophy, which is an increase in bulk without an increase in the number of cells. Cellular Adaptation of the pulp is typical.
    • Propagation Propagation Propagation refers to how the electrical signal spreads to every myocyte in the heart. Cardiac Physiology in lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs nodes and fast growth of blast cells/ necrosis Necrosis The death of cells in an organ or tissue due to disease, injury or failure of the blood supply. Ischemic Cell Damage are present in the histological sample.

Summary

If IM is suspected from history and physical examination, order a WBC count with differential and a heterophile test.

  • + heterophile: no further testing, confirmed diagnosis of IM
  • – heterophile: suggests cytomegalovirus Cytomegalovirus CMV is a ubiquitous double-stranded DNA virus belonging to the Herpesviridae family. CMV infections can be transmitted in bodily fluids, such as blood, saliva, urine, semen, and breast milk. The initial infection is usually asymptomatic in the immunocompetent host, or it can present with symptoms of mononucleosis. Cytomegalovirus (CMV) as a possible cause, but definitive diagnosis for EBV EBV Epstein-barr virus (EBV) is a linear, double-stranded DNA virus belonging to the herpesviridae family. This highly prevalent virus is mostly transmitted through contact with oropharyngeal secretions from an infected individual. The virus can infect epithelial cells and B lymphocytes, where it can undergo lytic replication or latency. Epstein-Barr Virus is serologic testing for EBV EBV Epstein-barr virus (EBV) is a linear, double-stranded DNA virus belonging to the herpesviridae family. This highly prevalent virus is mostly transmitted through contact with oropharyngeal secretions from an infected individual. The virus can infect epithelial cells and B lymphocytes, where it can undergo lytic replication or latency. Epstein-Barr Virus viral capsid Capsid The outer protein protective shell of a virus, which protects the viral nucleic acid. Capsids are composed of repeating units (capsomers or capsomeres) of capsid proteins which when assembled together form either an icosahedral or helical shape. Virology antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination via EBV EBV Epstein-barr virus (EBV) is a linear, double-stranded DNA virus belonging to the herpesviridae family. This highly prevalent virus is mostly transmitted through contact with oropharyngeal secretions from an infected individual. The virus can infect epithelial cells and B lymphocytes, where it can undergo lytic replication or latency. Epstein-Barr Virus antibody testing
Classic triad of im

Diagnostic algorithm for infectious mononucleosis

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Management

There is currently no specific antiviral Antiviral Antivirals for Hepatitis B therapy available, so treatment is supportive.

  • Symptomatic treatment includes: 
    • Rest from physical activity for 3 (non-contact sports) to 4 (contact sports) weeks after onset of initial symptoms to avoid splenic rupture Splenic rupture 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. Rupture of the Spleen
    • Antipyretics
    • Analgesics (e.g., acetaminophen Acetaminophen Acetaminophen is an over-the-counter nonopioid analgesic and antipyretic medication and the most commonly used analgesic worldwide. Despite the widespread use of acetaminophen, its mechanism of action is not entirely understood. Acetaminophen)
    • Nonsteroidal anti-inflammatory drugs
  • Administration of penicillin Penicillin Rheumatic Fever and aminopenicillins Aminopenicillins Penicillins can trigger Trigger The type of signal that initiates the inspiratory phase by the ventilator Invasive Mechanical Ventilation exanthema formation.

Prognosis Prognosis A prediction of the probable outcome of a disease based on a individual’s condition and the usual course of the disease as seen in similar situations. Non-Hodgkin Lymphomas

  • In normal cases, a favorable resolution is common and durable immunity is developed.
  • In patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with cellular immunodeficiencies and post-transplant patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship, more severe courses may occur. 
  • Chronic infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease are extremely rare.
  • Dormancy of virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology in B cells B cells Lymphoid cells concerned with humoral immunity. They are short-lived cells resembling bursa-derived lymphocytes of birds in their production of immunoglobulin upon appropriate stimulation. B cells: Types and Functions → increased risk for recurrence and B-cell lymphoma B-cell lymphoma A group of heterogeneous lymphoid tumors generally expressing one or more b-cell antigens or representing malignant transformations of B-lymphocytes. Selective IgA Deficiency in immunodeficient patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship (e.g., HIV HIV Anti-HIV Drugs patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship)
Amoxicillin rash

Amoxicillin Amoxicillin A broad-spectrum semisynthetic antibiotic similar to ampicillin except that its resistance to gastric acid permits higher serum levels with oral administration. Penicillins rash Rash Rocky Mountain Spotted Fever in patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with infectious mononucleosis

Image: “ Amoxicillin Amoxicillin A broad-spectrum semisynthetic antibiotic similar to ampicillin except that its resistance to gastric acid permits higher serum levels with oral administration. Penicillins rash Rash Rocky Mountain Spotted Fever in a patient with infectious mononucleosis (patient 4)” by Department of Dermatology and Allergology, University of Szeged, Szeged, Hungary. License: CC BY 4.0

Complications

Bacterial superinfection
Many patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship develop secondary streptococcal pharyngitis Pharyngitis 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. Pharyngitis.

Cardiac

  • Myocarditis Myocarditis 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. Myocarditis: inflammatory disease of the heart muscle, which mostly arises due to infection with cardiotropic viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology, especially infection with coxsackievirus Coxsackievirus 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. Coxsackievirus
  • Arrhythmias ( bradyarrhythmias Bradyarrhythmias 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. Bradyarrhythmias and tachyarrhythmias): disturbances in heart rhythm that affect the pumping efficiency of the heart muscle
  • Pericarditis Pericarditis 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. Pericarditis: inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the pericardium Pericardium A conical fibroserous sac surrounding the heart and the roots of the great vessels (aorta; venae cavae; pulmonary artery). Pericardium consists of two sacs: the outer fibrous pericardium and the inner serous pericardium. The latter consists of an outer parietal layer facing the fibrous pericardium, and an inner visceral layer (epicardium) resting next to the heart, and a pericardial cavity between these two layers. Heart: Anatomy resulting from infection, autoimmune disease, radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma, surgery, or myocardial infarction Myocardial infarction 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. Myocardial Infarction

Dermatologic

  • Ampicillin-associated rash Rash Rocky Mountain Spotted Fever
  • Oral hairy leukoplakia Leukoplakia Leukoplakia is a potentially malignant lesion affecting the squamous epithelium usually within the oral cavity. Leukoplakia can be associated with a history of chronic tobacco and alcohol use, both of which can synergistically damage the epithelium. Leukoplakia: triggered by EBV EBV Epstein-barr virus (EBV) is a linear, double-stranded DNA virus belonging to the herpesviridae family. This highly prevalent virus is mostly transmitted through contact with oropharyngeal secretions from an infected individual. The virus can infect epithelial cells and B lymphocytes, where it can undergo lytic replication or latency. Epstein-Barr Virus; results in white patches Patches Vitiligo on the tongue Tongue The tongue, on the other hand, is a complex muscular structure that permits tasting and facilitates the process of mastication and communication. The blood supply of the tongue originates from the external carotid artery, and the innervation is through cranial nerves. Lips and Tongue: Anatomy that may have a hairy appearance

Hematologic

  • Hemolytic anemia Hemolytic Anemia Hemolytic anemia (HA) is the term given to a large group of anemias that are caused by the premature destruction/hemolysis of circulating red blood cells (RBCs). Hemolysis can occur within (intravascular hemolysis) or outside the blood vessels (extravascular hemolysis). Hemolytic Anemia: type of anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview and Types caused by premature Premature Childbirth before 37 weeks of pregnancy (259 days from the first day of the mother’s last menstrual period, or 245 days after fertilization). Necrotizing Enterocolitis destruction of RBCs RBCs Erythrocytes, or red blood cells (RBCs), are the most abundant cells in the blood. While erythrocytes in the fetus are initially produced in the yolk sac then the liver, the bone marrow eventually becomes the main site of production. Erythrocytes: Histology. There is increased clearance by the spleen Spleen 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. Spleen: Anatomy (extravascular hemolytic anemia Hemolytic Anemia Hemolytic anemia (HA) is the term given to a large group of anemias that are caused by the premature destruction/hemolysis of circulating red blood cells (RBCs). Hemolysis can occur within (intravascular hemolysis) or outside the blood vessels (extravascular hemolysis). Hemolytic Anemia) or damage caused by a narrowed vascular lumen (intravascular hemolytic anemia Hemolytic Anemia Hemolytic anemia (HA) is the term given to a large group of anemias that are caused by the premature destruction/hemolysis of circulating red blood cells (RBCs). Hemolysis can occur within (intravascular hemolysis) or outside the blood vessels (extravascular hemolysis). Hemolytic Anemia).
  • Thrombocytopenia Thrombocytopenia 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. Thrombocytopenia: The normal range for platelet count is 150–400 X10⁹/L; thrombocytopenia Thrombocytopenia 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. Thrombocytopenia is a platelet count of less than 150 X10⁹/L.
  • Neutropenia Neutropenia Neutrophils are an important component of the immune system and play a significant role in the eradication of infections. Low numbers of circulating neutrophils, referred to as neutropenia, predispose the body to recurrent infections or sepsis, though patients can also be asymptomatic. Neutropenia: an abnormally low concentration of neutrophils Neutrophils Granular leukocytes having a nucleus with three to five lobes connected by slender threads of chromatin, and cytoplasm containing fine inconspicuous granules and stainable by neutral dyes. Innate Immunity: Phagocytes and Antigen Presentation (a type of WBC) in the blood
  • Aplastic anemia Aplastic Anemia 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. Aplastic Anemia: dysfunction of the hematopoietic cells ending in bone marrow Bone marrow The soft tissue filling the cavities of bones. Bone marrow exists in two types, yellow and red. Yellow marrow is found in the large cavities of large bones and consists mostly of fat cells and a few primitive blood cells. Red marrow is a hematopoietic tissue and is the site of production of erythrocytes and granular leukocytes. Bone marrow is made up of a framework of connective tissue containing branching fibers with the frame being filled with marrow cells. Bone Marrow: Composition and Hematopoiesis failure. Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship usually present with pancytopenia Pancytopenia Deficiency of all three cell elements of the blood, erythrocytes, leukocytes and platelets. Aplastic Anemia.

Hepatic

  • Reye’s syndrome: a rare disorder which results in brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification and liver Liver 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, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy damage that happens at any age, but mainly affects children
  • Mild viral hepatitis: infection that causes liver Liver 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, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation and damage,
  • Fulminant hepatic necrosis Necrosis The death of cells in an organ or tissue due to disease, injury or failure of the blood supply. Ischemic Cell Damage: more common in males and the most common cause of death in affected males

Splenic

  • Splenomegaly Splenomegaly Splenomegaly is pathologic enlargement of the spleen that is attributable to numerous causes, including infections, hemoglobinopathies, infiltrative processes, and outflow obstruction of the portal vein. Splenomegaly
  • Ruptured spleen Spleen 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. Spleen: Anatomy: occurs in < 0.5% of cases; more common in males. Presents with abrupt abdominal pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways, referred shoulder pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways, and hemodynamic compromise, and requires immediate surgery. Avoiding contact sports and heavy lifting can reduce risk.

Respiratory

  • Airway obstruction Airway obstruction 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). Airway Obstruction and difficulty breathing due to swollen tonsils Tonsils Tonsillitis (treat with steroids Steroids A group of polycyclic compounds closely related biochemically to terpenes. They include cholesterol, numerous hormones, precursors of certain vitamins, bile acids, alcohols (sterols), and certain natural drugs and poisons. Steroids have a common nucleus, a fused, reduced 17-carbon atom ring system, cyclopentanoperhydrophenanthrene. Most steroids also have two methyl groups and an aliphatic side-chain attached to the nucleus. Benign Liver Tumors)
  • Interstitial pneumonitis Pneumonitis Human Herpesvirus 6 and 7
  • Pneumonia Pneumonia 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. Pneumonia

Immunologic and Oncologic

  • Decreased cell-mediated immunity Cell-mediated immunity Manifestations of the immune response which are mediated by antigen-sensitized T-lymphocytes via lymphokines or direct cytotoxicity. This takes place in the absence of circulating antibody or where antibody plays a subordinate role. Squamous Cell Carcinoma (SCC)
  • Lymphoproliferative syndromes
  • Burkitt’s and non-Hodgkin’s lymphomas: associated with EBV EBV Epstein-barr virus (EBV) is a linear, double-stranded DNA virus belonging to the herpesviridae family. This highly prevalent virus is mostly transmitted through contact with oropharyngeal secretions from an infected individual. The virus can infect epithelial cells and B lymphocytes, where it can undergo lytic replication or latency. Epstein-Barr Virus infection. Endemic Burkitt’s lymphoma Lymphoma A general term for various neoplastic diseases of the lymphoid tissue. Imaging of the Mediastinum occurs mainly in Africa; the condition typically affects the jaw Jaw The jaw is made up of the mandible, which comprises the lower jaw, and the maxilla, which comprises the upper jaw. The mandible articulates with the temporal bone via the temporomandibular joint (TMJ). The 4 muscles of mastication produce the movements of the TMJ to ensure the efficient chewing of food. Jaw and Temporomandibular Joint: Anatomy and facial bones. Sporadic Sporadic Selective IgA Deficiency Burkitt’s lymphoma Lymphoma A general term for various neoplastic diseases of the lymphoid tissue. Imaging of the Mediastinum presents with abdominal masses or bone marrow Bone marrow The soft tissue filling the cavities of bones. Bone marrow exists in two types, yellow and red. Yellow marrow is found in the large cavities of large bones and consists mostly of fat cells and a few primitive blood cells. Red marrow is a hematopoietic tissue and is the site of production of erythrocytes and granular leukocytes. Bone marrow is made up of a framework of connective tissue containing branching fibers with the frame being filled with marrow cells. Bone Marrow: Composition and Hematopoiesis involvement.
  • Hodgkin’s lymphomas: cancer that originates from lymphocytes Lymphocytes Lymphocytes are heterogeneous WBCs involved in immune response. Lymphocytes develop from the bone marrow, starting from hematopoietic stem cells (HSCs) and progressing to common lymphoid progenitors (CLPs). B and T lymphocytes and natural killer (NK) cells arise from the lineage. Lymphocytes: Histology manifesting as non-painful enlarged lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs nodes in the neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess, under the arm Arm The arm, or “upper arm” in common usage, 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). Arm: Anatomy, or in the groin Groin The external junctural region between the lower part of the abdomen and the thigh. Male Genitourinary Examination

Neurologic

  • Encephalitis Encephalitis 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. Encephalitis: inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification, most commonly caused by a viral infection
  • Guillain-Barré syndrome Guillain-Barré syndrome 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). Guillain-Barré Syndrome: an auto-immune disorder that manifests as weakness and tingling Tingling Posterior Cord Syndrome in the extremities
  • Bell’s palsy Bell’s palsy A syndrome characterized by the acute onset of unilateral facial paralysis which progresses over a 2-5 day period. Weakness of the orbicularis oculi muscle and resulting incomplete eye closure may be associated with corneal injury. Pain behind the ear often precedes the onset of paralysis. This condition may be associated with Human Herpesvirus 1 infection of the facial nerve. Cranial Nerve Palsies: weakness or paralysis of the facial muscles Facial muscles The facial muscles (also called mimetic muscles) control facial expression and are supplied by the facial nerve. Most of them originate from the skull and attach to the skin around the facial openings, which serve as a method to group or classify them. Facial Muscles: Anatomy on one side of the face
  • Psychosis: false beliefs (delusions) and seeing or hearing things that others do not see or hear ( hallucinations Hallucinations Subjectively experienced sensations in the absence of an appropriate stimulus, but which are regarded by the individual as real. They may be of organic origin or associated with mental disorders. Schizophrenia)
  • Optic neuritis Optic neuritis Inflammation of the optic nerve. Commonly associated conditions include autoimmune disorders such as multiple sclerosis, infections, and granulomatous diseases. Clinical features include retro-orbital pain that is aggravated by eye movement, loss of color vision, and contrast sensitivity that may progress to severe visual loss, an afferent pupillary defect (Marcus-Gunn pupil), and in some instances optic disc hyperemia and swelling. Inflammation may occur in the portion of the nerve within the globe (neuropapillitis or anterior optic neuritis) or the portion behind the globe (retrobulbar neuritis or posterior optic neuritis). Cranial Nerve Palsies: inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the optic nerves
  • Transverse myelitis Myelitis Inflammation of the spinal cord. Relatively common etiologies include infections; autoimmune diseases; spinal cord; and ischemia. Clinical features generally include weakness, sensory loss, localized pain, incontinence, and other signs of autonomic dysfunction. Relapsing Fever: inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation which extends horizontally across the spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. 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). Spinal Cord: Anatomy, believed to be immune-mediated and triggered by infection; associated with signs and symptoms of motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology, sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology, and/or autonomic dysfunction Autonomic Dysfunction Anterior Cord Syndrome
  • Meningoencephalitis Meningoencephalitis Encephalitis: late-stage manifestation of tick-borne rickettsial diseases, such as Rocky Mountain spotted fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever and human monocytotropic ehrlichiosis Ehrlichiosis Ehrlichiosis is a tick-borne bacterial infection. The most common causative species include Ehrlichia chaffeensis, which infect and multiply within monocytes. The clinical presentation can vary widely, but often includes fever, malaise, headache, myalgia, and arthralgias. Ehrlichiosis and Anaplasmosis, caused by Ehrlichia chaffeensis Ehrlichia chaffeensis A species of gram-negative bacteria that is the causative agent of human ehrlichiosis. This organism was first discovered at fort chaffee, arkansas, when blood samples from suspected human ehrlichiosis patients were studied. Ehrlichiosis and Anaplasmosis
  • Cranial nerve palsies Cranial Nerve Palsies Cranial nerve palsy is a congenital or acquired dysfunction of 1 or more cranial nerves that will, in turn, lead to focal neurologic abnormalities in movement or autonomic dysfunction of its territory. Head/neck trauma, mass effect, infectious processes, and ischemia/infarction are among the many etiologies for these dysfunctions. Diagnosis is initially clinical and supported by diagnostic aids. Management includes both symptomatic measures and interventions aimed at correcting the underlying cause. Cranial Nerve Palsies: decrease or complete loss in function of 1 or more cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. The 12 Cranial Nerves: Overview and Functions. The etiology may be congenital Congenital Chorioretinitis or acquired.
  • Primary central nervous system Central nervous system The main information-processing organs of the nervous system, consisting of the brain, spinal cord, and meninges. Nervous System: Anatomy, Structure, and Classification lymphoma Lymphoma A general term for various neoplastic diseases of the lymphoid tissue. Imaging of the Mediastinum

Renal

  • Glomerulonephritis: inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of glomeruli that can be acute or chronic
  • Interstitial nephritis: spaces between tubules in kidneys Kidneys 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. Kidneys: Anatomy become inflamed, reducing the kidneys Kidneys 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. Kidneys: Anatomy‘ filtration abilities

Differential Diagnosis

The following conditions are differential diagnoses for infectious mononucleosis:

  • CMV infection: a double-stranded DNA DNA A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine). DNA Types and Structure virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology that is spread by secretions such as saliva Saliva The clear, viscous fluid secreted by the salivary glands and mucous glands of the mouth. It contains mucins, water, organic salts, and ptyalin. Salivary Glands: Anatomy, urine, and blood. Infection with CMV is usually asymptomatic in immunocompetent hosts but causes severe disease in immunocompromised immunocompromised A human or animal whose immunologic mechanism is deficient because of an immunodeficiency disorder or other disease or as the result of the administration of immunosuppressive drugs or radiation. Gastroenteritis patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship.
  • HIV infection HIV infection 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. HIV Infection and AIDS is caused by a single-stranded RNA RNA A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. RNA Types and Structure virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology of the Retroviridae Retroviridae 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. Human Immunodeficiency Virus (HIV) family and is transmitted through the exchange of body fluids such as semen and blood. HIV infection HIV infection 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. HIV Infection and AIDS causes a deterioration of the immune system Immune system The body’s defense mechanism against foreign organisms or substances and deviant native cells. It includes the humoral immune response and the cell-mediated response and consists of a complex of interrelated cellular, molecular, and genetic components. Primary Lymphatic Organs, beginning with constitutional symptoms Constitutional Symptoms Antineutrophil Cytoplasmic Antibody (ANCA)-Associated Vasculitis ( lymphadenopathy Lymphadenopathy Lymphadenopathy is lymph node enlargement (> 1 cm) and is benign and self-limited in most patients. Etiologies include malignancy, infection, and autoimmune disorders, as well as iatrogenic causes such as the use of certain medications. Generalized lymphadenopathy often indicates underlying systemic disease. Lymphadenopathy) and advancing into AIDS-defining illnesses (opportunistic infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease).
  • Streptococcal infection: gram-positive bacteria gram-positive bacteria Bacteria which retain the crystal violet stain when treated by gram’s method. Bacteriology known for their characteristic chain-like growth; can cause endocarditis Endocarditis 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. Endocarditis, meningitis Meningitis 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. Meningitis, bacterial pink eye, and necrotizing fasciitis Necrotizing fasciitis 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. Necrotizing Fasciitis
  • Toxoplasmosis Toxoplasmosis Toxoplasmosis is an infectious disease caused by Toxoplasma gondii, an obligate intracellular protozoan parasite. Felines are the definitive host, but transmission to humans can occur through contact with cat feces or the consumption of contaminated foods. The clinical presentation and complications depend on the host’s immune status. Toxoplasma/Toxoplasmosis: an infectious disease caused by Toxoplasma Toxoplasma Toxoplasmosis is an infectious disease caused by Toxoplasma gondii, an obligate intracellular protozoan parasite. Felines are the definitive host, but transmission to humans can occur through contact with cat feces or the consumption of contaminated foods. The clinical presentation and complications depend on the host’s immune status. Toxoplasma/Toxoplasmosis gondii, which is an obligate intracellular parasite that lives in the feline gut (definite host). Humans can become infected through the consumption of raw meat or food contaminated by cat feces. 
  • Parainfluenza viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology: enveloped RNA RNA A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. RNA Types and Structure viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology that can cause upper and lower respiratory infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease and croup Croup Croup, also known as laryngotracheobronchitis, is a disease most commonly caused by a viral infection that leads to severe inflammation of the upper airway. It usually presents in children < 5 years of age. Patients develop a hoarse, "seal-like" barking cough and inspiratory stridor. Croup, usually presenting as sudden myalgia Myalgia Painful sensation in the muscles. Ion Channel Myopathy/ arthralgia Arthralgia Pain in the joint. Rheumatic Fever with fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever and tonsillitis Tonsillitis Tonsillitis is inflammation of the pharynx or pharyngeal tonsils, and therefore is also called pharyngitis. An infectious etiology in the setting of tonsillitis is referred to as infectious pharyngitis, which is caused by viruses (most common), bacteria, or fungi. Tonsillitis
  • Diphtheria Diphtheria Diphtheria is an infectious disease caused by Corynebacterium diphtheriae that most often results in respiratory disease with membranous inflammation of the pharynx, sore throat, fever, swollen glands, and weakness. The hallmark sign is a sheet of thick, gray material covering the back of the throat. Diphtheria: a serious bacterial infection caused by Corynebacterium Corynebacterium Corynebacteria are gram-positive, club-shaped bacilli. Corynebacteria are commonly isolated on tellurite or Loeffler’s media and have characteristic metachromatic granules. The major pathogenic species is Corynebacterium diphtheriae, which causes a severe respiratory infection called diphtheria. Corynebacterium diphtheriae that affects the mucous membranes in the nose Nose The nose is the human body’s primary organ of smell and functions as part of the upper respiratory system. The nose may be best known for inhaling oxygen and exhaling carbon dioxide, but it also contributes to other important functions, such as tasting. The anatomy of the nose can be divided into the external nose and the nasal cavity. Nose and Nasal Cavity: Anatomy and throat Throat The pharynx is a component of the digestive system that lies posterior to the nasal cavity, oral cavity, and larynx. The pharynx can be divided into the oropharynx, nasopharynx, and laryngopharynx. Pharyngeal muscles play an integral role in vital processes such as breathing, swallowing, and speaking. Pharynx: Anatomy, resulting in sore throat Sore throat 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. Pharyngitis, fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, swollen glands, and weakness
  • Acute necrotizing ulcerative gingivitis Gingivitis Inflammation of gum tissue (gingiva) without loss of connective tissue. Chédiak-Higashi Syndrome: a common, non-contagious infection of the gums with sudden onset. Presents as painful, bleeding gums and ulceration Ulceration Corneal Abrasions, Erosion, and Ulcers of interdental papillae Papillae Lips and Tongue: Anatomy, with the development of necrosis Necrosis The death of cells in an organ or tissue due to disease, injury or failure of the blood supply. Ischemic Cell Damage and a dirty-gray pseudomembrane Pseudomembrane Candida/Candidiasis
  • Listeriosis: an infectious disease caused by the gram-positive Gram-Positive Penicillins bacterium Listeria monocytogenes Listeria monocytogenes 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 Monocytogenes/Listeriosis. Transmitted via contaminated food (especially raw milk), it presents asymptomatically, as a mild flu-like illness or febrile gastroenteritis Gastroenteritis 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. Gastroenteritis.

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