Autosomal Dominant Hyperimmunoglobulin E Syndrome

Epidemiology and Etiology

Epidemiology

• Incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency: 1/1,000,000 per year
• Males and females are affected equally.

Etiology

• Has been described in both sporadic Sporadic Selective IgA Deficiency and familial forms with an autosomal dominant Autosomal dominant Autosomal inheritance, both dominant and recessive, refers to the transmission of genes from the 22 autosomal chromosomes. Autosomal dominant diseases are expressed when only 1 copy of the dominant allele is inherited. Autosomal Recessive and Autosomal Dominant Inheritance inheritance pattern
• 60%–70% of cases are caused by mutations in the STAT3 gene Gene 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. Basic Terms of Genetics, which is responsible for the production of one of the signal transducers and activator of transcription Transcription Transcription of genetic information is the first step in gene expression. Transcription is the process by which DNA is used as a template to make mRNA. This process is divided into 3 stages: initiation, elongation, and termination. Stages of Transcription (STAT) 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. 
  • Mutations lead to the production of dysfunctional STAT3 protein (although produced in normal amounts) → defective immune response
  • Dysfunctional STAT3 blocks the maturation of immune cells, especially Th17 Th17 A subset of helper-effector T-lymphocytes which synthesize and secrete interleukins il-17; il-17f; and il-22. These cytokines are involved in host defenses and tissue inflammation in autoimmune diseases. T cells: Types and Functions cells → decreasing levels of interferon-gamma and interleukin-17 Interleukin-17 A proinflammatory cytokine produced primarily by T-lymphocytes or their precursors. Several subtypes of interleukin-17 have been identified, each of which is a product of a unique gene. Interleukins → abnormal neutrophil chemotaxis Chemotaxis The movement of leukocytes in response to a chemical concentration gradient or to products formed in an immunologic reaction. Leukocyte Adhesion Deficiency Type 1 → high susceptibility to 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, particularly bacterial and fungal 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 of the lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy and skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions 
  • STAT3 protein is also involved in the formation of cells that build and break down bone Bone 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. Bones: Structure and Types tissue → skeletal and dental abnormalities
• The cause of the other 30%–40% of cases is unknown.
• Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with autosomal dominant Autosomal dominant Autosomal inheritance, both dominant and recessive, refers to the transmission of genes from the 22 autosomal chromosomes. Autosomal dominant diseases are expressed when only 1 copy of the dominant allele is inherited. Autosomal Recessive and Autosomal Dominant Inheritance hyper-IgE syndrome (AD-HIES; also known as Job’s syndrome) also have abnormally high levels of IgE IgE An immunoglobulin associated with mast cells. Overexpression has been associated with allergic hypersensitivity. Immunoglobulins: Types and Functions (cause unknown) → eosinophilia

Clinical Presentation

Symptoms may be apparent at birth or become apparent during infancy or early childhood.

Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship present with various clinical manifestations and abnormalities:

• Characteristic facial features: broad nasal base and bridge, deep-set eyes, frontal Frontal The bone that forms the frontal aspect of the skull. Its flat part forms the forehead, articulating inferiorly with the nasal bone and the cheek bone on each side of the face. Skull: Anatomy bossing, irregularly proportioned cheeks Cheeks The part of the face that is below the eye and to the side of the nose and mouth. Melasma and jaws, midline anomalies, prognathism Prognathism A condition marked by abnormal protrusion of the mandible. Acromegaly and Gigantism, and generalized coarsening of the skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions (known as “coarse facies”)
• Dental: failure to shed primary teeth Teeth Normally, an adult has 32 teeth: 16 maxillary and 16 mandibular. These teeth are divided into 4 quadrants with 8 teeth each. Each quadrant consists of 2 incisors (dentes incisivi), 1 canine (dens caninus), 2 premolars (dentes premolares), and 3 molars (dentes molares). Teeth are composed of enamel, dentin, and dental cement. Teeth: Anatomy, leading to double rows of teeth Teeth Normally, an adult has 32 teeth: 16 maxillary and 16 mandibular. These teeth are divided into 4 quadrants with 8 teeth each. Each quadrant consists of 2 incisors (dentes incisivi), 1 canine (dens caninus), 2 premolars (dentes premolares), and 3 molars (dentes molares). Teeth are composed of enamel, dentin, and dental cement. Teeth: Anatomy
• Skeletal: scoliosis Scoliosis Scoliosis is a structural alteration of the vertebral column characterized by a lateral spinal curvature of greater than 10 degrees in the coronal plane. Scoliosis can be classified as idiopathic (in most cases) or secondary to underlying conditions. Scoliosis, joint hyperextensibility, osteoporosis Osteoporosis 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, and recurrent fractures Recurrent Fractures Osteogenesis Imperfecta 
• Ocular: xanthelasma Xanthelasma Primary Biliary Cholangitis, retinal detachment Retinal detachment Retinal detachment is the separation of the neurosensory retina from the retinal pigmented epithelium and choroid. Rhegmatogenous retinal detachment, the most common type, stems from a break in the retina, allowing fluid to accumulate in the subretinal space. Retinal Detachment, chalazion Chalazion A chalazion is one of the most common inflammatory lesions of the eyelid. It is caused by obstruction of the Meibomian or Zeis glands, leading to granulomatous inflammation and resulting in a firm, rubbery, slow-growing nodule that is typically non-tender. Chalazion, and strabismus Strabismus Strabismus is the misalignment of the eyes while fixating the gaze on an object. Strabismus can be idiopathic, but it may also be caused by cerebral palsy, uncorrected refractive errors, and extraocular muscle or cranial nerve dysfunction. Strabismus
• Respiratory: Recurrent lung 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 (most often by Staphylococcus Staphylococcus 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, Streptococcus Streptococcus Streptococcus is one of the two medically important genera of gram-positive cocci, the other being Staphylococcus. Streptococci are identified as different species on blood agar on the basis of their hemolytic pattern and sensitivity to optochin and bacitracin. There are many pathogenic species of streptococci, including S. pyogenes, S. agalactiae, S. pneumoniae, and the viridans streptococci. Streptococcus pneumoniae, and Haemophilus Haemophilus 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 pathogenic species are H. influenzae and H. ducreyi. Haemophilus influenzae) lead to air-filled cysts Cysts Any fluid-filled closed cavity or sac that is lined by an epithelium. Cysts can be of normal, abnormal, non-neoplastic, or neoplastic tissues. Fibrocystic Change ( pneumatoceles Pneumatoceles Pneumocystis jirovecii/Pneumocystis Pneumonia (PCP)) in the lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy and chronic respiratory insufficiency.
• Dermatologic: Staphylococcal 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 common, presenting as eczema-like rashes Rashes Rashes are a group of diseases that cause abnormal coloration and texture to the skin. The etiologies are numerous but can include irritation, allergens, infections, or inflammatory conditions. Rashes that present in only 1 area of the body are called localized rashes. Generalized rashes occur diffusely throughout the body. Generalized and Localized Rashes, blisters, scaling, open sores, pruritus Pruritus An intense itching sensation that produces the urge to rub or scratch the skin to obtain relief. Atopic Dermatitis (Eczema), and recurrent “cold” abscesses (lack cardinal signs of 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). 
• Immunological: increased susceptibility to 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 (e.g., mucocutaneous candidiasis Candidiasis 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. 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). Candida/Candidiasis) with very high levels of antibody IgE IgE An immunoglobulin associated with mast cells. Overexpression has been associated with allergic hypersensitivity. Immunoglobulins: Types and Functions and eosinophilia 
• Cardiovascular: thrombosis Thrombosis Formation and development of a thrombus or blood clot in the blood vessel. Epidemic Typhus, congenital Congenital Chorioretinitis patent ductus venosus Ductus venosus Development of the Heart, and coronary and aortic aneurysms
• Malignancies: lymphomas, such as anaplastic large cell lymphoma Lymphoma A general term for various neoplastic diseases of the lymphoid tissue. Imaging of the Mediastinum and peripheral T-cell lymphoma Lymphoma A general term for various neoplastic diseases of the lymphoid tissue. Imaging of the Mediastinum

Mnemonic

A helpful mnemonic of the clinical manifestations of AD-HIES is FATED: 

• F: Coarse or leonine Facies
• A: Cold staph Abscesses
• T: Retained primary Teeth
• E: Increased Ig Ig X-linked AgammaglobulinemiaE levels
• D: Dermatologic problems (e.g., eczema Eczema 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. Atopic Dermatitis (Eczema))

Diagnosis and Management

Diagnosis

The diagnosis of AD-HIES is based on clinical evaluation, especially a detailed patient history and identification Identification Defense Mechanisms of characteristic findings.

• Laboratory findings:
  • Elevated IgE IgE An immunoglobulin associated with mast cells. Overexpression has been associated with allergic hypersensitivity. Immunoglobulins: Types and Functions levels (> 2,000 IU/mL): diagnostic of AD-HIES
  • Eosinophilia on CBC > 2 standard deviations above the normal mean Mean Mean is the sum of all measurements in a data set divided by the number of measurements in that data set. Measures of Central Tendency and Dispersion
• Genetic testing Genetic Testing Detection of a mutation; genotype; karyotype; or specific alleles associated with genetic traits, heritable diseases, or predisposition to a disease, or that may lead to the disease in descendants. It includes prenatal genetic testing. Myotonic Dystrophies is available for STAT3 mutations.
• If symptoms of 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 are present, order computed tomography (CT) scans or X-rays X-rays 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. X-rays of the chest to detect lung 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 the development of pneumatoceles Pneumatoceles Pneumocystis jirovecii/Pneumocystis Pneumonia (PCP).

Management

There is no definitive cure. Management is aimed at treating symptoms as well as preventing and managing 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.

• Long-term anti-staphylococcal prophylactic antibiotic therapy 
• High-dose IV gammaglobulin and histamine-1 antagonists for eczema Eczema 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. Atopic Dermatitis (Eczema)
• Antibiotics and antifungal Antifungal Azoles agents, depending on the nature of 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, along with periodic chest imaging and high clinical suspicion for the early detection of recurrent infections Recurrent infections Common Variable Immunodeficiency (CVID)
• Surgery to drain abscesses
• Optimization of calcium Calcium A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes. Electrolytes and vitamin D Vitamin D A vitamin that includes both cholecalciferols and ergocalciferols, which have the common effect of preventing or curing rickets in animals. It can also be viewed as a hormone since it can be formed in skin by action of ultraviolet rays upon the precursors, 7-dehydrocholesterol and ergosterol, and acts on vitamin D receptors to regulate calcium in opposition to parathyroid hormone. Fat-soluble Vitamins and their Deficiencies intake to improve bone Bone 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. Bones: Structure and Types health
• Routine dental care
• Screening Screening Preoperative Care for scoliosis Scoliosis Scoliosis is a structural alteration of the vertebral column characterized by a lateral spinal curvature of greater than 10 degrees in the coronal plane. Scoliosis can be classified as idiopathic (in most cases) or secondary to underlying conditions. Scoliosis

Differential Diagnosis

The following conditions are differential diagnoses of autosomal dominant Autosomal dominant Autosomal inheritance, both dominant and recessive, refers to the transmission of genes from the 22 autosomal chromosomes. Autosomal dominant diseases are expressed when only 1 copy of the dominant allele is inherited. Autosomal Recessive and Autosomal Dominant Inheritance hyperimmunoglobulin E syndrome:

• Autosomal recessive Autosomal recessive Autosomal inheritance, both dominant and recessive, refers to the transmission of genes from the 22 autosomal chromosomes. Autosomal recessive diseases are only expressed when 2 copies of the recessive allele are inherited. Autosomal Recessive and Autosomal Dominant Inheritance hyper-IgE syndrome: a rare primary immunodeficiency Immunodeficiency Chédiak-Higashi Syndrome disorder characterized by recurrent pulmonary and dermatological 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 caused by bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology and 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. May present with abnormalities of the 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 or vessels but do not lack characteristic facial features and skeletal malformations. Can be due to mutations of the ZNF341, DOCK8, or PGM3 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.
• Cystic fibrosis Cystic fibrosis 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. Cystic Fibrosis: an autosomal recessive Autosomal recessive Autosomal inheritance, both dominant and recessive, refers to the transmission of genes from the 22 autosomal chromosomes. Autosomal recessive diseases are only expressed when 2 copies of the recessive allele are inherited. Autosomal Recessive and Autosomal Dominant Inheritance disorder caused by mutations in the CFTR gene Gene 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. Basic Terms of Genetics. Mutations lead to dysfunction of chloride Chloride Inorganic compounds derived from hydrochloric acid that contain the Cl- ion. Electrolytes channels Channels The Cell: Cell Membrane, which results in hyperviscous mucus and the accumulation of secretions. Common presentations include chronic 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, failure to thrive Failure to Thrive Failure to thrive (FTT), or faltering growth, describes suboptimal weight gain and growth in children. The majority of cases are due to inadequate caloric intake; however, genetic, infectious, and oncological etiologies are also common. Failure to Thrive, and pancreatic insufficiency. 
• Chronic granulomatous disease Chronic Granulomatous Disease Chronic granulomatous disease (CGD), as the name implies, is a chronic disorder that is characterized by granuloma formation. This disorder is a consequence of defective phagocytic cells that are unable to produce bactericidal superoxide because of a defect in nicotinamide adenine dinucleotide phosphate (NADPH), the oxidase responsible for the respiratory burst in phagocytic leukocytes. Chronic Granulomatous Disease: a chronic disorder that is characterized by granuloma formation. This disorder is a consequence of dysfunctional phagocytic cells that are unable to produce bactericidal Bactericidal Penicillins superoxide due to a defect in nicotinamide adenine dinucleotide phosphate Nicotinamide adenine dinucleotide phosphate Nicotinamide adenine dinucleotide phosphate. A coenzyme composed of ribosylnicotinamide 5′-phosphate (nmn) coupled by pyrophosphate linkage to the 5′-phosphate adenosine 2. Pentose Phosphate Pathway ( NADPH NADPH Nicotinamide adenine dinucleotide phosphate. A coenzyme composed of ribosylnicotinamide 5′-phosphate (nmn) coupled by pyrophosphate linkage to the 5′-phosphate adenosine 2. Pentose Phosphate Pathway) oxidase Oxidase Neisseria in these cells. Presentation includes recurrent skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions 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, 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, and 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.
• Atopic dermatitis Atopic Dermatitis 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. Atopic Dermatitis (Eczema): also known as allergic eczema Eczema 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. Atopic Dermatitis (Eczema), a chronic pruritic inflammatory skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions disease that occurs most frequently in children, but also in adults. Often associated with elevated IgE IgE An immunoglobulin associated with mast cells. Overexpression has been associated with allergic hypersensitivity. Immunoglobulins: Types and Functions and a personal or family history Family History Adult Health Maintenance of atopy Atopy Atopic Dermatitis (Eczema). Presents with intense pruritus Pruritus An intense itching sensation that produces the urge to rub or scratch the skin to obtain relief. Atopic Dermatitis (Eczema), papulovesicular lesions Papulovesicular Lesions Atopic Dermatitis (Eczema) on extensor surfaces, and lichenification Lichenification Atopic Dermatitis (Eczema) on flexural areas
• 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 and AIDS AIDS 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. HIV Infection and AIDS: 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 in 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. Transmitted through the exchange of body fluids such as semen and blood. Presentation is marked by 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 such as 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 such as 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.