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Type I leprosy reaction
Type I leprosy reaction, or reversal reaction, is a type IV hypersensitivity response to Mycobacterium leprae antigens in borderline leprosy, causing inflamed skin lesions and neuritis; about 95% of cases occur within two years of starting multidrug therapy.
Type I vestibular sensory cell
Type I vestibular sensory cell (type I hair cell): amniote-only flask-shaped vestibular hair cell enveloped by a calyx afferent terminal, with low-voltage-activated K+ currents and both quantal and non-quantal transmission, unlike bouton-innervated type II cells.
Type II hypersensitivity
Type II hypersensitivity (antibody-mediated cytotoxic hypersensitivity) is tissue injury caused by IgG or IgM antibodies binding cell-surface or extracellular-matrix antigens, via complement, phagocytosis, or ADCC; examples include autoimmune hemolytic anemia, transfusion reactions, Goodpasture syndrome, and pemphigus.
Type III hypersensitivity
Type III hypersensitivity (immune complex disease), a Gell and Coombs class, in which IgG/IgM bind soluble antigen; deposited complexes activate complement, causing Arthus reaction, serum sickness, SLE, and glomerulonephritis.
Type IV hypersensitivity
Type IV hypersensitivity (delayed-type hypersensitivity) is T cell-mediated, antibody-independent inflammation peaking 48-72 hours after antigen re-exposure; examples include contact dermatitis, SJS/TEN, DRESS, tuberculin reaction, and transplant rejection, diagnosed by patch testing.
Types of seizures
The types of seizures are classified by the ILAE as focal onset, generalized onset, or unknown onset, based on where the seizure begins in the brain.
TYPHIBEV
TYPHIBEV (TyphiBEV), typhoid conjugate vaccine by Biological E, India; Vi-CRM197, single 0.5 mL dose, ages 6 months to 45 years; WHO prequalified 4 December 2020, non-inferior to Typbar TCV.
Typhoid fever
Typhoid fever (enteric fever) is a systemic infection caused by Salmonella Typhi, spread fecal-orally via contaminated food or water. Key facts: blood-culture diagnosis, under 1% treated fatality, 1–4% chronic carriers, GBD 2017 estimate 14.3 million enteric fever cases, WHO-recommended conjugate vaccine, XDR strain REPJPP01 from Pakistan.
Typhoid peritonitis
Typhoid peritonitis, peritoneal inflammation from typhoid intestinal perforation in Salmonella Typhi infection, typically after 2–3 weeks of illness; treated surgically with lavage and broad-spectrum antibiotics, with case fatality around 15% globally.
Typhoid vaccine
Typhoid vaccine protects against Salmonella Typhi. WHO recommends TCV, Vi polysaccharide, and oral Ty21a; TCV single-dose efficacy about 83% at 2 years; first vaccines date to 1896.
Typical antipsychotic
Typical (first-generation) antipsychotics such as chlorpromazine and haloperidol are dopamine D2 receptor antagonists introduced in the 1950s; distinguished from atypicals by higher extrapyramidal side-effect risk above roughly 80% D2 occupancy.
Typical nemaline myopathy
Typical nemaline myopathy (ORPHA:171436) is the most common, moderate neonatal form of nemaline myopathy, with facial and skeletal muscle weakness, mild respiratory involvement, and ACTA1, NEB, or TPM2 mutations.
Tyrer–Cuzick model
The Tyrer–Cuzick model, also called the IBIS model, is a statistical tool that estimates a woman's 10-year and lifetime risk of developing breast cancer to guide screening and prevention.
Tyropanoic acid
Tyropanoic acid (tyropanoate, Bilopaque), a triiodinated oral X-ray contrast medium for cholecystography, synthesized 1962 from iopanoic acid, FDA-approved 1969, now discontinued.
Tyrosine kinase inhibitor therapy
Tyrosine kinase inhibitor (TKI) therapy is targeted drug treatment with small molecules that block the ATP-binding site of tyrosine kinases, stopping the signaling cancer cells use to grow and survive.
Tyrosinemia type 1
Tyrosinemia type 1 (HT-1, hepatorenal tyrosinemia) is an autosomal recessive FAH-deficiency disorder causing liver and kidney damage, neurologic crises, and HCC risk; treated with nitisinone and a low-tyrosine diet.
Tyrosinemia type 2
Tyrosinemia type 2 (Richner-Hanhart syndrome, oculocutaneous tyrosinemia) is a rare autosomal recessive disorder caused by TAT gene deficiency at 16q22.2, causing corneal dystrophy, painful palmoplantar hyperkeratosis, and intellectual disability in about half of cases, treated with a tyrosine- and phenylalanine-restricted diet.
Tyrosinemia type 3
Tyrosinemia type 3 is a rare inherited disorder of tyrosine metabolism caused by HPD enzyme deficiency, marked by high blood tyrosine and, in some cases, intellectual disability and seizures.
Tyrothricin
Tyrothricin, a peptide antibiotic complex from Brevibacillus parabrevis discovered by René Dubos in 1939, mixes tyrocidines and gramicidins; first mass-produced antibiotic, topical use only due to hemolytic toxicity.
Tzanck test
Tzanck test (Tzanck smear), a bedside cytology test devised by Arnault Tzanck in 1947: blister-base cells are stained and examined for multinucleated giant cells in herpes and acantholytic cells in pemphigus; cheap, rapid, high specificity, lower sensitivity than PCR.
U-138MG
U-138MG, also written U138 or U-138 MG, is a human cancer cell line from a malignant brain glioma, established in 1968 and widely used in glioblastoma research.
U-373MG ATCC
U-373MG ATCC (CVCL_2219, HTB-17) is a human glioblastoma/astrocytoma cell line shown by STR profiling and sequencing to be a U-251MG derivative, not the original 1973 Uppsala U-373MG line; ICLAC-00295, ATCC distribution discontinued.
U-47700
U-47700 (trans-3,4-dichloro-N-[2-(dimethylamino)cyclohexyl]-N-methylbenzamide) is a non-fentanyl synthetic opioid, a selective μ-opioid receptor agonist developed by Upjohn in the 1970s, about 7.5 times more potent than morphine, linked to overdose deaths and scheduled in Schedule I (US CSA, 2016; UN Single Convention 61/I, 2017).
U-ENDURE trial
U-ENDURE (NCT03345823) is AbbVie's phase 3, 52-week randomized withdrawal maintenance trial of oral upadacitinib 15 mg and 30 mg versus placebo in Crohn's disease responders to U-EXCEL/U-EXCEED induction, showing superior clinical remission and endoscopic response.
UA022 (KRAS G12D inhibitor)
UA022 is a preclinical KRAS G12D inhibitor discovered by Chinese biotech 祐森健恒 and exclusively licensed worldwide to AstraZeneca in November 2023 for $24 million upfront plus up to $395 million in milestones.
UB-221
UB-221 (CUE-221, Ascendant-221) is a humanized anti-IgE IgG1 monoclonal antibody, humanized from mouse clone 8D6, that binds IgE Cε3, neutralizes free IgE, and uniquely spares CD23-mediated IgE downregulation; in Phase 2 CSU trials it beat placebo and outperformed omalizumab.
Ublituximab
Ublituximab (Briumvi) is a glycoengineered chimeric anti-CD20 IgG1 monoclonal antibody by TG Therapeutics for relapsing multiple sclerosis, approved in the US (2022), EU (2023), and Australia (2025), given as one-hour infusions every 24 weeks.
Ubrogepant
Ubrogepant (Ubrelvy), oral CGRP receptor antagonist (gepant) by Allergan/AbbVie, FDA-approved 2019 for acute migraine with or without aura in adults; 50-100 mg dosing, CYP3A4 interactions, first oral CGRP antagonist approved.
UBT251
UBT251 is a long-acting triple agonist of the GLP-1, GIP, and glucagon receptors developed by United Biotechnology (TUL) and licensed to Novo Nordisk in March 2025; phase 2 trials in China showed up to 19.7% weight loss at 24 weeks in obesity and HbA1c reduction up to 2.16% in type 2 diabetes.
Udenafil
Udenafil (Zydena, DA-8159) is a Korean-developed oral PDE5 inhibitor for erectile dysfunction, launched by Dong-A Pharmaceutical in 2005; 100-200 mg doses, about 12-hour duration, not FDA-approved.