Life and health

Fitusiran

Fitusiran (Qfitlia), an antithrombin-lowering siRNA by Sanofi/Alnylam, FDA-approved March 28, 2025 for bleeding prophylaxis in hemophilia A or B with or without inhibitors, dosed subcutaneously every two months.

Fitz-Hugh–Curtis syndrome

Fitz-Hugh–Curtis syndrome, or perihepatitis, is inflammation of the liver capsule from pelvic inflammatory disease, causing right upper quadrant pain and violin-string adhesions; mainly caused by Chlamydia trachomatis, affecting 4–14% of females with PID.

Fitzroya

Fitzroya (alerce, lahuán, Fitzroya cupressoides) is a monotypic Patagonian cypress genus of Chile and Argentina; an Endangered, CITES-listed conifer living over 3,600 years, reaching 4–5 m diameter, with only 15% of original forest remaining.

Five prime untranslated region

The 5′ UTR (five prime untranslated region) is the mRNA segment between the cap and start codon that governs translation initiation via Kozak context, uORFs, secondary structure, IRESs, and riboswitches, and is engineered in mRNA therapeutics.

Five Tibetan Rites

Five Tibetan Rites, also called the Five Tibetans or Fountain of Youth: five dynamic yoga-like exercises, up to 21 repetitions each, published by Peter Kelder in The Eye of Revelation (1939); Tibetan origin disputed, evidence limited.

Five-prime cap

Five-prime cap (m7GpppN): N7-methylguanosine joined 5′-to-5′ to eukaryotic and viral mRNA, added co-transcriptionally by triphosphatase, guanylyltransferase, and methyltransferase; cap-0/1/2 variants, decay, immunity, and vaccine capping methods.

FIX-Chagas trial

FIX-Chagas (NCT05519046) is a randomized InCor Heart Institute trial in São Paulo comparing cardiac contractility modulation with CRT in 60 patients with Chagas cardiomyopathy, heart failure, and non-left bundle branch block.

Fixation (histology)

Fixation (histology): tissue preservation from autolysis, chiefly by formaldehyde/formalin crosslinking. Key facts: 10% neutral buffered formalin standard, 4% PFA, 6–48 h HER2 window, antigen retrieval, freezing alternative.

Fixation index

The fixation index, written F ST, is a population genetics statistic measuring genetic differentiation among subpopulations, introduced by Sewall Wright in work published in 1931 and 1943.

Fixed cutaneous sporotrichosis

Fixed cutaneous sporotrichosis (ICD-11 1F2J.1) is the localized, non-lymphatic form of Sporothrix skin infection, about 25% of cutaneous cases, treated with itraconazole 200 mg daily for 3-6 months.

Fixed drug eruption

Fixed drug eruption (FDE): a cutaneous adverse drug reaction recurring at the same skin site on re-exposure, caused by epidermal CD8+ memory T cells; severe variant GBFDE has 15.2% mortality.

Fixed Orthodontic Appliances

Fixed orthodontic appliances (braces) attach brackets to teeth with an arch wire to move teeth. From Fauchard's 1728 bandolet and Angle's Edgewise bracket to bonding, Ni-Ti wires, and self-ligating brackets.

Fixed subaortic stenosis

Fixed subaortic stenosis (subvalvular aortic stenosis, SAS): congenital fibromuscular or membranous obstruction of the left ventricular outflow tract below the aortic valve, usually presenting before age 10, treated by surgical resection with substantial recurrence risk.

FKBP1A

FKBP1A (FKBP12, calstabin1) encodes the 12-kDa FK506-binding peptidyl-prolyl isomerase, receptor for tacrolimus and rapamycin, inhibitor complex partner of calcineurin and mTOR, and stabilizing subunit of ryanodine receptor calcium-release channels.

FKBP4

FKBP4 (FKBP52, FKBP59, Hsp56) is a human chromosome 12 gene encoding an FK506-binding immunophilin PPIase and Hsp90 co-chaperone that enables glucocorticoid, androgen, and progesterone receptor nuclear translocation.

FKBP5

FKBP5 (FKBP prolyl isomerase 5, protein FKBP51) is a human chromosome 6p21 gene encoding an FK506-binding glucocorticoid receptor co-chaperone whose variants interact with early-life stress to raise risk of depression and PTSD.

FKRP-related limb-girdle muscular dystrophy R9

FKRP-related limb-girdle muscular dystrophy R9 (LGMDR9, formerly LGMD2I) is an autosomal recessive dystroglycanopathy from FKRP mutations impairing alpha-dystroglycan glycosylation, causing progressive proximal weakness, cardiomyopathy, and respiratory involvement; the c.826C>A founder mutation is common in Scandinavia and the UK.

Sep 29, 2026

FLACC scale

The FLACC scale, standing for Face, Legs, Activity, Cry, and Consolability, is an observational pain scale for infants and young children, scoring five behaviors from 0 to 10.

Flaccid hemiplegia

Flaccid hemiplegia (ICD-11 MB53.1, ICD-10-CM G81.0) is one-sided paralysis with limp, low-tone muscles, seen acutely after cortical or internal capsule lesions and sometimes permanent.

Flaccid paralysis

Flaccid paralysis, also called acute flaccid paralysis (AFP), is loss of muscle tone from lower motor neuron lesions, caused by Guillain-Barré syndrome, poliomyelitis, acute flaccid myelitis, transverse myelitis, botulism, or myopathies, and tracked by WHO polio surveillance.

Flaccid tetraplegia

Flaccid tetraplegia is paralysis of all four limbs with limp, toneless muscles, unlike the stiffness of spastic tetraplegia; it typically reflects lower motor neuron damage or acute spinal shock.