National Center for Advancing and Translational Sciences Genetic and Rare Diseases Information Center, a program of the National Center for Advancing and Translational Sciences

Trimethylaminuria

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Other Names:
TMAU; Fish odor syndrome; Fish malodor syndrome; TMAU; Fish odor syndrome; Fish malodor syndrome; Stale fish syndrome; TMAuria See More
Categories:
Trimethylaminuria is a metabolic disorder that occurs when the body is unable to break down certain nitrogen-containing compounds such as trimethylamine. Trimethylamine, which has a fishy odor, is produced in the intestines when certain types of food (i.e. eggs, liver, legumes, fish and some vegetables) are digested. As trimethylamine begins to accumulate in the body, it is released in the sweat, urine, reproductive fluids, and breath. This leads to the characteristic odor of trimethylaminuria. Affected individuals do not have other health problems related to the condition, but the unpleasant odor can result in social and psychological problems. Trimethylaminuria seems to be more common in women. Researchers think this may be due to higher hormone levels aggravating symptoms of the disorder.[1]

Trimethylaminuria is often caused by changes (mutations) in the FMO3 gene and is inherited in an autosomal recessive manner. Although there is no cure, trimethylaminuria can often be managed by reducing the amount of trimethylamine in the body. For example, affected people can modify their diet to avoid foods with high levels of trimethylamine.[2][3]
Last updated: 2/27/2018
Trimethylaminuria is characterized primarily by a fishy odor that occurs when excess trimethylamine is released in the person's sweat, urine, reproductive fluids, and breath. Although some affected people may have a constant strong odor, most have a moderate odor that can vary in intensity. Factors that promote sweating, such as exercise, stress, and emotional upsets, may worsen the odor. In females, symptoms may be more severe right before and during menstruation, after taking oral contraceptives, or around the time of menopause.[2][3]

Affected people typically do not have any additional signs and symptoms and appear healthy. However, the odor can interfere with many aspects of daily life, leading to social and psychological problems.[2][3]
Last updated: 2/27/2018

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Showing of 9 |
Medical Terms Other Names
Learn More:
HPO ID
Percent of people who have these symptoms is not available through HPO
Anemia
Low number of red blood cells or hemoglobin
0001903
Autosomal recessive inheritance 0000007
Depressivity
Depression
0000716
Hypertension 0000822
Neutropenia
Low blood neutrophil count
Low neutrophil count
[ more ] 		0001875
Recurrent pneumonia 0006532
Splenomegaly
Increased spleen size
0001744
Tachycardia
Fast heart rate
Heart racing
Racing heart
[ more ] 		0001649
Trimethylaminuria
High urine trimethylamine levels
0003614
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Last updated: 7/1/2020
Most cases of trimethylaminuria are caused by changes (mutations) in the FMO3 gene. This gene provides the body with instructions to make an enzyme that is responsible for breaking down certain nitrogen-containing compounds such as trimethylamine. Trimethylamine is produced in the intestines when certain types of food (i.e. eggs, liver, legumes, fish and some vegetables) are digested. A mutation in this gene prevents the enzyme from working properly, so it is unable to break down compounds like trimethylamine. As trimethylamine begins to build up in the body, it is released in a person's sweat, urine, and breath. Because trimethylamine has a fishy odor, this leads to the characteristic features of trimethylaminuria.[2]

In some instances, trimethylaminuria may occur in people who do not have changes in both copies of the FMO3 gene. In these people, trimethylaminuria may be caused by having high levels of trimethylamine due to the presence of more trimethylamine-producing bacteria in the gut. High levels of trimethylamine could also be due to a diet high in foods that create trimethylamine as they are metabolized (broken down). In some cases, people with a change in only one copy of the FMO3 gene may have milder symptoms of trimethylaminuria.[2] 
Last updated: 2/27/2018
Trimethylaminuria is inherited in an autosomal recessive manner.[2] This means that to be affected, a person must have a mutation in both copies of the responsible gene in each cell. The parents of an affected person usually each carry one mutated copy of the gene and are referred to as carriers. Carriers typically do not show signs or symptoms of the condition, but in some cases carriers of trimethylaminuria may have mild symptoms or have temporary episodes of fish-like odor.[1] When two carriers of an autosomal recessive condition have children, each child has a 25% (1 in 4) risk to have the condition, a 50% (1 in 2) risk to be a carrier like each of the parents, and a 25% chance to not have the condition and not be a carrier.
Last updated: 2/27/2018
A diagnosis of trimethylaminuria is often suspected based on the presence of characteristic signs and symptoms. A urine test and genetic testing can then be ordered to confirm the diagnosis. The urine test measures the level of trimethylamine in the urine, as affected individuals would be expected to have high trimethylamine urine levels. This test may be done after a person is given a dose of choline by mouth.[3][4]

Genetic testing is available for FMO3, the gene known to cause trimethylaminuria.[3] Carrier testing for at-risk relatives and prenatal testing are possible if the disease-causing mutations in the family are known.

GeneReviews offers more specific information about the diagnosis of trimethylaminuria. To access this resource, please click here.
Last updated: 1/24/2017

Testing Resources

  • The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.
  • The Monell Chemical Senses Center is able to assist in the diagnostic testing of patients who may have trimethylaminuria. Monell is a non-profit, basic scientific research center focused on understanding the senses of taste and smell. They are not a medical clinic. If you are interested in more information, you can send an e-mail to bodyodorinfo@monell.org. The Information Center provides the names of these centers for informational purposes only, not as an endorsement of the institutions' products or services.
Although there is no cure for trimethylaminuria, the following are some ways to reduce symptoms of odor:[1][3]
  • Avoidance of foods that contain trimethylamine and its precursors (choline, lecithin, and trimethylamine N-oxide). Trimethylamine is present in high levels in milk obtained from wheat-fed cows. Choline is present in high amounts in: eggs, liver, kidney, peas, beans, peanuts, soy products, brussels sprouts, broccoli, cabbage, and cauliflower. Trimethylamine N-oxide is present in seafood   
  • Low doses of antibiotics. This decreases the amount of trimethylamine that is made by bacteria in the intestines   
  • Laxatives can decrease the amount of time food remains in the intestines and therefore reduce the amount of trimethylamine made   
  • Nutritional supplements (activated charcoal and copper chlorophyllin) can decrease the concentration of trimethylamine in the urine
  • Soaps with a moderate pH (between 5.5 and 6.5) can help remove the secreted trimethylamine from the skin
  • Riboflavin (vitamin B2) supplements can enhance any existing FMO3 enzyme activity (which breaks down trimethylamine)   
  • Avoidance of exercise, stress, emotional upsets, and other factors that can promote sweating
People with trimethylaminuria may also find the following to be helpful:[1]
  • Behavioral counseling to help with depression and other psychological symptoms
  • Genetic counseling to better understand how they developed trimethylaminuria and the risks of passing the condition on to their children

NOTE: People should follow the treatment advice of their healthcare provider and should not attempt to self-administer these treatment approaches. Medications and supplements can have unintended interactions, and dietary restrictions can result in nutritional deficits.
Last updated: 2/27/2018
In general, the long-term outlook (prognosis) for people with trimethylaminuria is good. Affected people have a normal life expectancy and aside from the fishy odor, the condition is typically not associated with other health problems.

Although some cases (especially those that are mild or moderate) can be successfully managed with a restricted diet, the odor can interfere with aspects of daily life. Consequently, many people affected by this condition struggle with depression and other psychological problems.[3][2]
Last updated: 2/27/2018

If you need medical advice, you can look for doctors or other healthcare professionals who have experience with this disease. You may find these specialists through advocacy organizations, clinical trials, or articles published in medical journals. You may also want to contact a university or tertiary medical center in your area, because these centers tend to see more complex cases and have the latest technology and treatments.

If you can’t find a specialist in your local area, try contacting national or international specialists. They may be able to refer you to someone they know through conferences or research efforts. Some specialists may be willing to consult with you or your local doctors over the phone or by email if you can't travel to them for care.

You can find more tips in our guide, How to Find a Disease Specialist. We also encourage you to explore the rest of this page to find resources that can help you find specialists.

Healthcare Resources

Research helps us better understand diseases and can lead to advances in diagnosis and treatment. This section provides resources to help you learn about medical research and ways to get involved.

Clinical Research Resources

  • The U.S. National Institutes of Health, through the National Library of Medicine, developed ClinicalTrials.gov to provide patients, family members, and members of the public with current information on clinical research studies. There is a study titled Pediatric Patients With Metabolic or Other Genetic Disorders which may be of interest to you.

Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

Social Networking Websites

  • RareConnect has an online community for patients and families with this condition so they can connect with others and share their experiences living with a rare disease. The project is a joint collaboration between EURORDIS (European Rare Disease Organisation) and NORD (National Organization for Rare Disorders).

Living with a genetic or rare disease can impact the daily lives of patients and families. These resources can help families navigate various aspects of living with a rare disease.

Community Resources

  • The Job Accommodation Network (JAN) has information on workplace accommodations and disability employment issues related to this condition. JAN is a service of the Office of Disability Employment Policy in the U.S. Department of Labor.

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • Genetics Home Reference (GHR) contains information on Trimethylaminuria. This website is maintained by the National Library of Medicine.
  • The National Human Genome Research Institute's (NHGRI) website has an information page on this topic. NHGRI is part of the National Institutes of Health and supports research on the structure and function of the human genome and its role in health and disease.
  • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

In-Depth Information

  • GeneReviews provides current, expert-authored, peer-reviewed, full-text articles describing the application of genetic testing to the diagnosis, management, and genetic counseling of patients with specific inherited conditions.
  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Trimethylaminuria. Click on the link to view a sample search on this topic.
  • The United States Department of Agriculture lists the choline content of common foods in their USDA Food Composition Database. The web site was jointly developed by the USDA Nutrient Data Laboratory, and the Food and Nutrition Information Center and Information Systems Division of the National Agricultural Library.

Questions sent to GARD may be posted here if the information could be helpful to others. We remove all identifying information when posting a question to protect your privacy. If you do not want your question posted, please let us know.

  1. Learning about Trimethylaminuria. National Human Genome Research Institute. July 2011; http://www.genome.gov/11508983.
  2. Trimethylaminuria. Genetics Home Reference. January 2013; http://ghr.nlm.nih.gov/condition=trimethylaminuria.
  3. Phillips I & Shephard E. Trimethylaminuria. GeneReviews. 2015; http://www.ncbi.nlm.nih.gov/books/NBK1103/.
  4. Trimethylaminuria. NORD. August 2014; https://www.rarediseases.org/rare-disease-information/rare-diseases/byID/997/viewAbstract.