Fish Odor Syndrome (Trimethylaminuria) (cont.)

How common is fish odor syndrome (trimethylaminuria)?

Trimethylaminuria is an uncommon genetic disorder; its incidence is unknown.

What genes are related to fish odor syndrome (trimethylaminuria)?

Mutations in the FMO3 gene cause trimethylaminuria.

The FMO3 gene provides instructions for making an enzyme that breaks down nitrogen-containing compounds from the diet, including trimethylamine. This compound is produced by bacteria in the intestine as they help digest proteins from eggs, liver, legumes (such as soybeans and peas), certain kinds of fish, 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 processed properly and can build up in the body. As excess trimethylamine 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.

How do people inherit fish odor syndrome (trimethylaminuria)?

Most cases of trimethylaminuria appear to be inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. Most often, the parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but typically do not show signs and symptoms of the condition. Carriers of an FMO3 mutation, however, may have mild symptoms of trimethylaminuria or experience temporary episodes of fish-like body odor.


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