Definition of Fish odor syndrome Fish-odor syndrome: An inborn
error of metabolism that is associated with an offensive body
odor whose scent is similar to the smell of rotting fish. Fish-
odor syndrome is due to the excessive excretion of
trimethylamine (TMA) in urine, sweat, and breath. This syndrome
is caused by a mutation in the gene for the enzyme flavin-
containing monooxygenase-3 (FMO3). Dietary modifications to
reduce the consumption of triethylamine precursors may provide
some relief of symptoms. Also known as trimethylaminuria. Last
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