Trimethylaminuria

Trimethylaminuria, often called fish odor syndrome, is a rare inherited metabolic disorder in which the body cannot properly break down trimethylamine, a strong-smelling compound produced during digestion of certain foods. In someone without the condition, an enzyme called flavin-containing monooxygenase 3 converts trimethylamine into an odorless compound, trimethylamine oxide. When this enzyme is defective or produced in insufficient amounts, trimethylamine instead builds up and is released through a person's urine, sweat and breath, producing a persistent smell resembling rotting fish. The primary, genetic form of the disorder follows an autosomal recessive inheritance pattern and stems from mutations in the FMO3 gene on chromosome 1, of which more than forty variants have been documented; a secondary form can also occur without any underlying genetic mutation when the body is simply overwhelmed by dietary trimethylamine.