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Genetics Home Reference: your guide to understanding genetic conditions
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Trimethylaminuria

Reviewed January 2013

What is trimethylaminuria?

Trimethylaminuria is a disorder in which the body is unable to break down trimethylamine, a chemical compound that has a pungent odor. Trimethylamine has been described as smelling like rotting fish, rotting eggs, garbage, or urine. As this compound builds up in the body, it causes affected people to give off a strong odor in their sweat, urine, and breath. The intensity of the odor may vary over time. The odor can interfere with many aspects of daily life, affecting a person's relationships, social life, and career. Some people with trimethylaminuria 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. This 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 during the digestion of proteins from eggs, liver, legumes (such as soybeans and peas), certain kinds of fish, and other foods. Normally, the FMO3 enzyme converts strong-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 odor characteristic of trimethylaminuria. Researchers believe that stress and diet also play a role in triggering symptoms.

Although FMO3 gene mutations account for most cases of trimethylaminuria, the condition can also be caused by other factors. The strong body odor may result from an excess of certain proteins in the diet or from an abnormal increase in bacteria that produce trimethylamine in the digestive system. A few cases of the disorder have been identified in adults with liver or kidney disease. Temporary symptoms of this condition have been reported in a small number of premature infants and in some healthy women at the start of menstruation.

Related Gene(s)

Changes in this gene are associated with trimethylaminuria.

  • FMO3

How do people inherit 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 strong body odor.

Where can I find information about diagnosis or management of trimethylaminuria?

These resources address the diagnosis or management of trimethylaminuria and may include treatment providers.

  • Gene Review: Trimethylaminuria (http://www.ncbi.nlm.nih.gov/books/NBK1103)
  • Genetic Testing Registry: Trimethylaminuria (http://www.ncbi.nlm.nih.gov/gtr/conditions/C0342739)
  • Monell Chemical Senses Center: TMAU & Body Malodors (http://www.monell.org/contact_us/tmau/)
  • National Human Genome Research Institute: Diagnosis and Treatment of Trimethylaminuria (http://www.genome.gov/11508983)

You might also find information on the diagnosis or management of trimethylaminuria in Educational resources and Patient support.

General information about the diagnosis (http://ghr.nlm.nih.gov/handbook/consult/diagnosis) and management (http://ghr.nlm.nih.gov/handbook/consult/treatment) of genetic conditions is available in the Handbook. Read more about genetic testing (http://ghr.nlm.nih.gov/handbook/testing), particularly the difference between clinical tests and research tests (http://ghr.nlm.nih.gov/handbook/testing/researchtesting).

To locate a healthcare provider, see How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.

Where can I find additional information about trimethylaminuria?

You may find the following resources about trimethylaminuria helpful. These materials are written for the general public.

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

What other names do people use for trimethylaminuria?

  • fish malodor syndrome
  • fish odor syndrome
  • stale fish syndrome
  • TMAU
  • TMAuria

For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines (http://ghr.nlm.nih.gov/ConditionNameGuide) and How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.

What if I still have specific questions about trimethylaminuria?

Ask the Genetic and Rare Diseases Information Center (https://rarediseases.info.nih.gov/gard).

What glossary definitions help with understanding trimethylaminuria?

autosomal ; autosomal recessive ; bacteria ; cell ; compound ; depression ; digestion ; digestive ; digestive system ; enzyme ; gene ; incidence ; inherited ; intestine ; kidney ; menstruation ; molecule ; mutation ; recessive ; stress ; syndrome ; trimethylamine

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.

References

  • Chalmers RA, Bain MD, Michelakakis H, Zschocke J, Iles RA. Diagnosis and management of trimethylaminuria (FMO3 deficiency) in children. J Inherit Metab Dis. 2006 Feb;29(1):162-72. (http://www.ncbi.nlm.nih.gov/pubmed/16601883?dopt=Abstract)
  • Christodoulou J. Trimethylaminuria: an under-recognised and socially debilitating metabolic disorder. J Paediatr Child Health. 2012 Mar;48(3):E153-5. doi: 10.1111/j.1440-1754.2010.01978.x. Epub 2011 Jan 31. Review. (http://www.ncbi.nlm.nih.gov/pubmed/21276117?dopt=Abstract)
  • Hernandez D, Addou S, Lee D, Orengo C, Shephard EA, Phillips IR. Trimethylaminuria and a human FMO3 mutation database. Hum Mutat. 2003 Sep;22(3):209-13. Review. (http://www.ncbi.nlm.nih.gov/pubmed/12938085?dopt=Abstract)
  • Mitchell SC, Smith RL. Trimethylaminuria: the fish malodor syndrome. Drug Metab Dispos. 2001 Apr;29(4 Pt 2):517-21. (http://www.ncbi.nlm.nih.gov/pubmed/11259343?dopt=Abstract)
  • Mitchell SC. Trimethylaminuria: susceptibility of heterozygotes. Lancet. 1999 Dec 18-25;354(9196):2164-5. (http://www.ncbi.nlm.nih.gov/pubmed/10609842?dopt=Abstract)
  • National Human Genome Research Institute (http://www.genome.gov/11508983)
  • Shephard EA, Treacy EP, Phillips IR. Clinical utility gene card for: trimethylaminuria. Eur J Hum Genet. 2012 Mar;20(3). doi: 10.1038/ejhg.2011.214. Epub 2011 Nov 30. (http://www.ncbi.nlm.nih.gov/pubmed/22126753?dopt=Abstract)
  • Shimizu M, Cashman JR, Yamazaki H. Transient trimethylaminuria related to menstruation. BMC Med Genet. 2007 Jan 27;8:2. (http://www.ncbi.nlm.nih.gov/pubmed/17257434?dopt=Abstract)
  • Wise PM, Eades J, Tjoa S, Fennessey PV, Preti G. Individuals reporting idiopathic malodor production: demographics and incidence of trimethylaminuria. Am J Med. 2011 Nov;124(11):1058-63. doi: 10.1016/j.amjmed.2011.05.030. Epub 2011 Aug 16. (http://www.ncbi.nlm.nih.gov/pubmed/21851918?dopt=Abstract)
  • Yamazaki H, Fujieda M, Cashman JR, Kamataki T. Mild trimethylaminuria observed in a Japanese cohort with liver damage. Am J Med. 2005 Jul;118(7):803-5. (http://www.ncbi.nlm.nih.gov/pubmed/15989923?dopt=Abstract)
  • Zschocke J, Kohlmueller D, Quak E, Meissner T, Hoffmann GF, Mayatepek E. Mild trimethylaminuria caused by common variants in FMO3 gene. Lancet. 1999 Sep 4;354(9181):834-5. (http://www.ncbi.nlm.nih.gov/pubmed/10485731?dopt=Abstract)

 

The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.

 
Reviewed: January 2013
Published: September 1, 2015