Increased concentration of trimethylamine in the urine.

Primary trimethylaminuria is characterized by a fishy odor resembling that of rotten or decaying fish that results from excess excretion of trimethylamine in the urine, breath, sweat, and reproductive fluids. No physical symptoms are associated with trimethylaminuria. Affected individuals appear normal and healthy; however, the unpleasant odor often results in social and psychological problems. Symptoms are usually present from birth and may worsen during puberty. In females, symptoms are more severe just before and during menstruation, after taking oral contraceptives, and around the time of menopause.

Trimethylaminuria causes the body to produce a fishy odor that is released in the sweat, urine, breath, and reproductive fluids. People with trimethylaminuria are unable to break down trimethylamine, a chemical found in certain foods. The excess trimethylamine builds up and is the source of the odor. There are no other physical symptoms...