Trimethylaminuria is a disorder in which the volatile, fish-smelling compound,
trimethylamine (TMA) accumulates and is excreted in the urine, but is also found in the sweat and breath of these patients. Because many patients have associated body odours or
halitosis,
trimethylaminuria sufferers can meet serious difficulties in a social context, leading to other problems such as isolation and depression. TMA is formed by bacteria in the mammalian gut from reduction of compounds such as
trimethylamine-N-oxide (
TMAO) and
choline. Primary
trimethylaminuria sufferers have an inherited
enzyme deficiency where TMA is not efficiently converted to the non-odorous
TMAO in the liver. Secondary causes of
trimethylaminuria have been described, sometimes accompanied by genetic variations. Diagnosis of
trimethylaminuria requires the measurement of TMA and
TMAO in urine, which should be collected after a high substrate meal in milder or intermittent cases, most simply, a marine-fish meal. The symptoms of
trimethylaminuria can be improved by changes in the diet to avoid precursors, in particular
TMAO which is found in high concentrations in marine fish. Treatment with
antibiotics to control bacteria in the gut, or
activated charcoal to sequester TMA, may also be beneficial.