1500+ medical terms, defined.

Vibrio parahaemolyticus is a halophilic, gram-negative curved rod that causes acute gastroenteritis after consumption of raw or undercooked seafood, especially oysters. It presents with watery diarrhea, abdominal cramps, nausea, and vomi...

Guarnieri bodies are eosinophilic cytoplasmic inclusion bodies found in the epithelial cells of skin lesions in patients infected with poxviruses, classically smallpox (Variola virus) and vaccinia virus. They represent sites of viral rep...

Cowdry bodies are eosinophilic intranuclear inclusion bodies seen in cells infected with certain viruses, most notably Herpes Simplex Virus (HSV) and Varicella-Zoster Virus (VZV). They represent aggregates of viral proteins and nucleic a...

Icosahedral describes a symmetric geometric capsid shape (20 triangular faces, 12 vertices) used by many viruses to package their genome efficiently. It is a key virology term for classifying viruses on USMLE exams, distinguishing them f...

Herpetic gingivostomatitis is a primary infection with herpes simplex virus type 1 (HSV-1), most commonly seen in young children, presenting with painful vesicular/ulcerative lesions on the gingiva, tongue, and oral mucosa, along with fe...

Isotretinoína (13-cis-retinoic acid) es un retinoide oral usado para el tratamiento del acné nodular/quístico severo refractario a otras terapias. Es altamente teratogénico y requiere estrictas medidas de control de embarazo. Reduce el t...

Isotretinoin is an oral retinoid (vitamin A derivative) used to treat severe, refractory nodulocystic acne. It reduces sebaceous gland size and sebum production but is highly teratogenic, requiring strict pregnancy prevention protocols (...

Streptomycin is an aminoglycoside antibiotic that inhibits bacterial protein synthesis by binding the 30S ribosomal subunit, causing misreading of mRNA. It is historically important as the first effective drug against tuberculosis and is...

Anticardiolipin antibodies (aCL) are a subtype of antiphospholipid antibodies (IgG/IgM/IgA) that target cardiolipin, a phospholipid found in cell membranes and mitochondria. They are a key diagnostic criterion for antiphospholipid syndro...

Keratoconjunctivitis is inflammation of both the cornea (keratitis) and conjunctiva (conjunctivitis), presenting with eye redness, pain, photophobia, tearing, and foreign body sensation. Common causes include viral infections (especially...

Teres major is a muscle of the posterior shoulder that adducts, extends, and internally (medially) rotates the arm at the glenohumeral joint. It originates from the inferior angle of the scapula and inserts on the medial lip of the inter...

Carbol fuchsin (carbolfuchsin) is a red dye used primarily in the Ziehl-Neelsen and Kinyoun acid-fast staining techniques to identify acid-fast bacteria such as Mycobacterium tuberculosis and Nocardia. It contains basic fuchsin dissolved...

Fas ligand (FasL, CD95L) is a type II transmembrane protein of the TNF family that binds Fas (CD95) death receptor to trigger extrinsic apoptosis. It is critical for immune homeostasis, killing of virus-infected/tumor cells by cytotoxic...

Fas (CD95) is a cell-surface death receptor that triggers apoptosis via the extrinsic (death receptor) pathway when bound by its ligand FasL. It plays a crucial role in immune homeostasis, peripheral tolerance, and elimination of activat...

Paucibacillary refers to a form of leprosy (Hansen's disease) characterized by a low bacterial load, typically presenting with fewer than 5 skin lesions and negative or minimal acid-fast bacilli on skin smears. It correlates with the tub...

GIP (Glucose-dependent Insulinotropic Peptide, also called Gastric Inhibitory Peptide) is an incretin hormone secreted by K cells in the duodenum and jejunum in response to fat and glucose ingestion. Its primary function is to stimulate...

Hib refers to Haemophilus influenzae type b, an encapsulated gram-negative coccobacillus that historically caused invasive pediatric infections such as meningitis, epiglottitis, and septic arthritis. Widespread Hib conjugate vaccination...

Alveolarization is the developmental process by which primary saccules of the fetal/neonatal lung are subdivided by secondary septation to form mature alveoli, dramatically increasing surface area for gas exchange. It occurs primarily du...

Human papillomavirus (HPV) is a non-enveloped, double-stranded DNA virus that infects epithelial cells and is the most common sexually transmitted infection. Low-risk strains (6, 11) cause genital warts (condylomata acuminata), while hig...

Hepatitis B virus (HBV) is a hepatotropic DNA virus (Hepadnaviridae) transmitted via blood, sexual contact, and perinatally. It causes acute and chronic hepatitis and is a major risk factor for cirrhosis and hepatocellular carcinoma. Ser...

Poliomyelitis is an acute viral infection caused by poliovirus (an enterovirus), which can lead to destruction of anterior horn motor neurons in the spinal cord, causing asymmetric flaccid paralysis. Most infections are asymptomatic or c...

Granulomatosis infantiseptica is a disseminated form of congenital listeriosis characterized by widespread microabscesses and granulomas in multiple organs (liver, spleen, lungs, skin, adrenal glands) due to transplacental transmission o...

Ecthyma gangrenosum is a cutaneous lesion classically associated with Pseudomonas aeruginosa bacteremia, typically occurring in immunocompromised or neutropenic patients. It presents as a hemorrhagic pustule that evolves into a necrotic...

FKBP (FK506-binding protein) is a family of immunophilin proteins with peptidyl-prolyl isomerase activity that bind immunosuppressant drugs, most notably tacrolimus (FK506) and sirolimus. FKBP12 is the key isoform involved in mediating t...

TGF-α (Transforming Growth Factor-alpha) is a peptide growth factor that binds the epidermal growth factor receptor (EGFR/HER1) to stimulate epithelial cell proliferation and tissue development. It plays roles in normal wound healing and...

HLA (Human Leukocyte Antigen) genes are the human version of the Major Histocompatibility Complex (MHC), located on chromosome 6. They encode cell-surface proteins responsible for presenting peptide antigens to T cells, playing a central...

TLR4 (Toll-like receptor 4) is a pattern recognition receptor on innate immune cells that recognizes lipopolysaccharide (LPS) from gram-negative bacterial cell walls. It triggers NF-κB activation, leading to pro-inflammatory cytokine rel...

CD14 is a glycosylphosphatidylinositol (GPI)-anchored surface receptor found mainly on monocytes/macrophages that acts as a co-receptor for bacterial lipopolysaccharide (LPS). It works with LPS-binding protein (LBP) and TLR4/MD-2 to trig...

CD18 is the beta-2 (β2) integrin subunit that pairs with various alpha subunits (CD11a, b, c) to form leukocyte adhesion molecules such as LFA-1 and Mac-1. Mutations in the ITGB2 gene encoding CD18 cause Leukocyte Adhesion Deficiency typ...

LFA-1 (Lymphocyte Function-associated Antigen-1) is a β2 integrin (CD11a/CD18) expressed on leukocytes that binds ICAM-1 on endothelial cells, mediating firm adhesion during leukocyte extravasation. It is critical for immune cell traffic...

Cromolyn sodium is a mast cell stabilizer used as prophylaxis for asthma and allergic conditions, preventing degranulation and release of histamine and other mediators. It has no role in acute bronchospasm treatment due to slow onset, an...

Nedocromil is a mast cell stabilizer used prophylactically for asthma, similar in mechanism to cromolyn sodium. It prevents mast cell degranulation, thereby inhibiting release of histamine and other inflammatory mediators. It is not effe...

The intermediomedial nucleus (substantia intermedia medialis) is a group of interneurons located in the intermediate gray zone of the spinal cord, adjacent to the central canal, and is involved in autonomic (visceral afferent) processing.

Sialyl-Lewis X (sLeX) is a fucosylated, sialylated tetrasaccharide expressed on the surface of leukocytes that mediates their initial rolling adhesion to activated vascular endothelium. It binds to selectins (E-, P-, and L-selectin) duri...

Factor XII (Hageman factor) is a zymogen that initiates the intrinsic (contact activation) coagulation pathway upon exposure to negatively charged surfaces. It is activated by contact with collagen, basement membrane, or activated platel...

Hageman factor, also known as Factor XII, is a coagulation protein that initiates the intrinsic (contact activation) pathway of the coagulation cascade. It is activated upon contact with negatively charged surfaces (e.g., collagen, suben...

Insulin glulisine (Apidra) is a rapid-acting insulin analog used to control postprandial glucose spikes in diabetes management. It has a faster onset and shorter duration of action compared to regular human insulin, mimicking physiologic...

Lispro is a rapid-acting insulin analog used to control postprandial blood glucose in diabetes mellitus. It has a faster onset (10-15 min) and shorter duration of action (3-4 hours) compared to regular insulin, making it ideal for mealti...

PALS (Pediatric Advanced Life Support) is a standardized set of protocols for the emergency management of critically ill infants and children, including recognition and treatment of respiratory failure, shock, and cardiac arrest. It emph...

The periarteriolar lymphatic sheath (PALS) is the T-cell-rich region of the white pulp of the spleen, surrounding the central arterioles. It is the site where antigen-presenting cells present antigens to T lymphocytes, initiating cell-me...

UDP-glucuronosyltransferase (UGT) is a phase II drug-metabolizing enzyme that conjugates glucuronic acid to lipophilic substrates (drugs, bilirubin, hormones) to increase water solubility for excretion. It is located in the smooth endopl...

Coltivirus is a genus of double-stranded RNA viruses in the family Reoviridae (Sedoreoviridae), transmitted by ticks (Dermacentor andersoni), that causes Colorado tick fever—a self-limited febrile illness endemic to the Rocky Mountain re...

Amiloride is a potassium-sparing diuretic that blocks the epithelial sodium channel (ENaC) in the principal cells of the collecting duct. It reduces sodium reabsorption and secondarily decreases potassium and hydrogen ion secretion, maki...

Lassa virus is an Old World arenavirus endemic to West Africa, transmitted via aerosolized rodent excreta (Mastomys natalensis) or contact with infected body fluids. It causes Lassa fever, a viral hemorrhagic fever ranging from asymptoma...

Pathognomonic refers to a specific sign, symptom, or finding that is so characteristic of a particular disease that its presence definitively indicates that diagnosis. Unlike sensitive findings, pathognomonic signs are highly specific bu...

Hydrophobia (fear of water/water-avoidance) is a classic symptom of rabies encephalitis, caused by severe painful spasms of the pharyngeal and laryngeal muscles triggered by attempts to swallow water. It reflects brainstem dysfunction fr...

Aerophobia (fear of drafts of air or fear of swallowing/choking on air) is a classic, highly specific clinical sign of rabies encephalitis, along with hydrophobia. It results from painful, involuntary spasms of pharyngeal and laryngeal m...

Warthin-Finkeldey giant cells are multinucleated giant cells found in the lymphoid tissue (tonsils, lymph nodes) of patients with measles (rubeola) infection. They are pathognomonic for measles and represent virus-induced cell fusion. Th...

Nursemaid's elbow (radial head subluxation) is a common pediatric injury seen in children aged 1-4 years, caused by axial traction on an extended, pronated arm (e.g., pulling/swinging a child by the hand). The annular ligament slips over...

Melioidosis is an infectious disease caused by Burkholderia pseudomallei, a gram-negative bacillus found in soil and water in Southeast Asia and Northern Australia. It causes a wide spectrum of disease from localized skin infections to s...