Rare autosomal-recessive inherited metabolic disorder due to mutations in the FMO3 gene, preventing the breakdown of trimethylamine (TMA) by gut bacteria. Can also be an acquired disorder. Characterized by a strong fishy odor in urine, sweat, breath, and other hormonal or reproductive excretions. May present from birth and worsen at puberty. Management consists of restricting intake of foods containing TMA precursors: marine fish, liver, kidney, eggs, brussel sprouts, cauliflower, peanuts, beans, peas, and milk from grass-fed cows. Treatments are available, including antibiotics, lotions, supplements, and counseling.