Trimethylaminuria (TMAU) – FMO3 sequencing

Diagnostic Use

Primary FMO3 deficiency, an inborn error of choline metabolism, leads to an accumulation of trimethylamine, which because of its associated pungent odour of rotting fish, is a socially crippling disorder. Onset is generally in early childhood, but it may take years before the diagnosis is established. The disorder is inherited as an autosomal recessive trait as a consequence of mutations in the FMO3 gene. At least 20 different disease-causing mutations have been identified. The incidence of TMAU due to FMO3 deficiency is not precisely known, but may range from 1 in 100 to 1 in 1000 individuals. Management of this disorder is primarily dietary.

Genotyping is appropriate only following a positive biochemical screening result - see Trimethylamine, Urine testing for further details.


Genetics - Molecular Pathology

Delphic Registration Code



Fish odour syndrome
FMO3 sequencing

Turnaround Time

4 weeks