Syndrome, fish-odor: An inborn error of metabolism associated with an offensive body odor, the smell of rotting fish, due to the excessive excretion of trimethylaminuria (TMA) in urine, sweat, and breath. Persons with TMA may experience tachycardia (fast heart rate) and severe hypertension (high blood pressure) after eating cheese (which contains tyramine) and after using nasal sprays containing epinephrine. TMA is caused by a mutation (change) in the gene for an enzyme, flavin-containing monooxygenase-3 (FMO3) encoded by a gene on chromosome #1. The FMO3 enzyme metabolizes tyramine (which is in cheese). The syndrome is associated with various psychosocial reactions, including social isolation, clinical depression and attempted suicide.