Trimethylaminuria
Trimethylaminuria (TMAU), also known as fish odor syndrome or fish malodor syndrome, is a rare metabolic disorder that causes a defect in the normal production of an enzyme named flavin-containing monooxygenase 3 (FMO3). When FMO3 is not working correctly or if not enough enzyme is produced, the body loses the ability to properly convert trimethylamine (TMA) from precursor compounds in food digestion into trimethylamine oxide (TMAO), through a process called N-oxidation. Trimethylamine then builds up and is released in the person's sweat, urine, and breath, giving off a fishy odor. Primary trimethylaminuria is caused by genetic mutations that affect the FMO3 function of the liver. Symptoms matching TMAU can also occur when there is no genetic cause, yet excessive TMA is excreted - this has been described as secondary trimethylaminuria (TMAU2). Metabolic pathway Trimethylamine enters the body via the consumption of certain foods and supplements: When food is consumed that contains TMA and/or TMAO (predominately seafood; saltwater fish, shellfish, seaweed and kelp). TMAO is converted by bacteria in the lower gastrointestinal tract (gut) into TMA. When a food substance, supplement or medicine that contains a TMA precursor (choline or carnitine) is ingested. Some precursor is absorbed into the bloodstream in