What is trimethylaminuria?
Trimethylaminuria is a disorder in which the body is unable to break down trimethylamine, a compound derived from the diet that has a strong odor of rotting fish. As trimethylamine builds up in the body, it causes affected people to give off a fish-like odor in their sweat, urine, and breath. The intensity of this odor may vary over time. In many cases, the strong body odor interferes with an affected person's relationships, social life, and career. People with trimethylaminuria may experience depression and social isolation as a result of this condition.
How common is trimethylaminuria?
Trimethylaminuria is an uncommon genetic disorder; its incidence is unknown.
What genes are related to trimethylaminuria?
Mutations in the FMO3 gene cause trimethylaminuria.
The FMO3 gene makes an enzyme that breaks down nitrogen-containing compounds from the diet, including trimethylamine. This compound is produced by bacteria in the intestine as they digest proteins from eggs, meat, soy, and other foods. Normally, the FMO3 enzyme converts fishy-smelling trimethylamine into another molecule that has no odor. If the enzyme is missing or its activity is reduced because of a mutation in the FMO3 gene, trimethylamine is not broken down and instead builds up in the body. As the compound is released in a person's sweat, urine, and breath, it causes the strong odor characteristic of trimethylaminuria. Researchers believe that stress and diet also play a role in triggering symptoms.
Although FMO3 mutations account for most known cases of trimethylaminuria, some cases are caused by other factors. A fish-like body odor could result from an excess of certain proteins in the diet or from an increase in bacteria that normally break down trimethylamine in the digestive system. A few cases of the disorder have been identified in adults with liver damage caused by hepatitis (an inflammation of the liver). Temporary symptoms of trimethylaminuria have also been reported in a small number of premature infants and in some healthy women at the start of menstruation.
How do people inherit trimethylaminuria?
Most cases of trimethylaminuria appear to be inherited in an autosomal recessive pattern, which means two copies of the gene in each cell are altered. Most often, the parents of an individual with an autosomal recessive disorder are carriers of one copy of the altered gene. Carriers may have mild symptoms of trimethylaminuria or experience temporary episodes of fish-like body odor