(fish odor syndrome)

Very rare. Mutation of a gene located on 1q23-q25 near those of the FMO1 to FMO4 and FMO6: these microsomal enzymes have a protective role against xenobiotics. This results in the total absence (homozygous) or intermittent decrease in activity (heterozygous) of the NADPH-dependent flavoprotein monooxygenase (FMO3) that transforms the trimethylamine into trimethylamine-N-oxide. FMO3 is primarily located in the liver and brain. This anomaly causes no physical abnormality but a permanent (homozygous) or intermittent (heterozygous in case of intake of trimethylamine) excretion of trimethylamine in body secretions (breath, sweat, urine, saliva) which then have a characteristic odour of rotten fish. In humans, trimethylamine is mainly of intestinal origin due to bacterial action on food.

Anesthetic implications:

nothing major; avoid the formation of trimethylamine, e.g.: stress and pharmacological agents that may be producing trimethylamine such as tertiary amines such as lidocaine and bupivacaine, cimetidine, ranitidine, nicotine and some benzodiazepines.

References : 

• Astuto M, Arena G, Ferla L, Murabito P, Gullo A. 
  Perioperative recommendations in a child with Fish Odor syndrome. 
  Pediatr Anesth 2009; 19: 926-7.

Updated: September 2018