Genetic and Rare Diseases Information Center (GARD)


Other names people use for this condition
  • TMAU
  • Fish odor syndrome
  • Fish malodor syndrome
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Trimethylaminuria
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I think I may have trimethylaminuria. I would like more information that could be shared with my doctor that could help my doctor in diagnosing the condition.



  • What is trimethylaminuria? (Back to Top)

  • Trimethylaminuria is a metabolic disorder in which an individual is not able to break down trimethylamine into smaller compounds. Trimethylamine is the compound that gives fish their fishy odor. Trimethylaminuria, has been around for centuries, but has only gained scientific recognition and support in the past 30 years.[1]
  • Last Reviewed: 2/11/2009

  • What are the symptoms of trimethylaminuria? (Back to Top)

  • Trimethylamine accumulates in the body of patients with trimethylaminuria. The trimethylamine gets released in the person's sweat, urine, reproductive fluids, and breath, giving off a strong fishy odor. Some people with trimethylaminuria have a strong odor all the time, but most have a moderate smell that varies in intensity over time. Individuals with this condition do not have any physical symptoms, and typically appear healthy.[2]
  • Last Reviewed: 2/11/2009

  • Is trimethylaminuria more common in certain populations? (Back to Top)

  • The syndrome seems to be more common in women than men, but scientists don't know why.[1] Scientists suspect that female sex hormones, such as progesterone and/or estrogen, aggravate symptoms.[1] There are several reports that the condition worsens around puberty. In women, symptoms can worsen just before and during menstrual periods, after taking oral contraceptives, and around menopause.[2]

  • Last Reviewed: 2/11/2009

  • What causes trimethylaminuria? (Back to Top)

  • People with trimethylaminuria lack the enzyme flavin-containing monooxygenase 3 (FMO3), which is produced by the liver and is part of a family of similar enzymes responsible for breaking down compounds that contain nitrogen, sulfur, or phosphorous.[3] This enzyme is produced by the FMO3 gene. Not all of the functions of the FMO3 enzyme are known, so physicians don't know what other symptoms besides odor may be associated with trimethylaminuria.[1][2]
  • Last Reviewed: 2/11/2009

  • Is trimethylaminuria inherited? (Back to Top)

  • Yes. Trimethylaminuria is usually inherited in an autosomal recessive fashion, which means that two mutated (faulty) genes are usually needed for a person to have symptoms. Both parents of an individual with trimethylaminuria are “carriers” of the condition, in other words, they both carry one copy of an altered gene for trimethylaminuria (see diagram below).[1]

    Autosomal Recessive


    Since this condition usually requires two altered genes to cause symptoms, typically neither parent of an individual with trimethylaminuria have any symptoms.   Occasionally, however, “carriers” of one copy of an FMO3 mutation may experience mild symptoms of trimethylaminuria or have temporary episodes of fish-like odor.[1]

    There are several mutations, or alterations in the gene that is associated with autosomal recessively inherited trimethylaminuria.  Most of the mutations are nonsense mutations in the 1q23-q25 region of chromosome 1, where the gene that codes for flavin-containing monooxygenase 3 (FMO3) is located. FMO3 is the enzyme involved in breaking down trimethylamine (the compound responsible for the fish odor). Due to the variability of symptoms people with trimethylaminuria experience, researchers hypothesize that a variety of genetic mutations that have not yet been discovered can influence the symptoms of the disease, affecting time of onset and how strong the odor is. They also suspect that stress and diet play a role in triggering symptoms.[1][2][3]


  • Last Reviewed: 2/11/2009

  • Is testing available for trimethylaminuria? (Back to Top)

  • Yes. Diagnostic testing for trimethylaminuria is conducted by a urine test that measures the percentage of total trimethylamine that is excreted.[2] Urine testing should be performed on two separate occasions when the individual is on a non-restricted diet.[2] In addition to urine testing, carrier testing is also available for trimethylaminuria. This test is called either a 'TMA challenge' or a 'TMA load' test. It involves giving an individual a 600mg capsule of trimethylamine. Carriers of trimethylaminuria excrete 20-30% of total trimethylamine as the free unmetabolized amine, while non-carriers excrete less than 13%.[2]

    The laboratories listed below provide clinical diagnostic testing for elevated levels of trimethylamine in the urine. The Information Center provides the names of these centers for informational purposes only, not as an endorsement of the institutions' products or services. Please note that some laboratories do not accept direct contact from patients. Therefore, we recommend that you work with a medical or genetics professional to contact these laboratories for further information.

    Univeristy of Colorodo Helath Sciences Center
    Contact: Dr. Susan Tjoa
    Phone: 303-315-8175
    E-mail: susan.tjoa@uchsc.edu

    The Human Biomolecular Research Institute
    5310 Eastgate Mall
    San Diego, CA 92121
    Phone: 858-458-9305
    Fax: 858-458-9311
    Email: rhandley@hbri.org
    Web site: http://www.hbri.org/

    Monell Chemical Senses Center
    University of Pennsylvania
    Phone: 267-519-4700
    Contact: George Preti, PhD 
    E-mail: preti@monell.org  
    Web site: http://www.monell.org/tmau_h.htm
    For more information, patients can send an e-mail to: bodyodorinfo@monell.org.

    In addition to urine testing, gene sequencing to look for mutations in the FMO3 gene is available.[2]  Click here to view the contact information for laboratories conducting genetic testing for trimethylaminuria.  Once again, please note that most laboratories do not accept direct contact from patients and their families; therefore, you will need to work with a health care provider if you are interested in learning more. 
  • Last Reviewed: 2/11/2009

  • What treatment is available for trimethylaminuria? (Back to Top)

  • Although there is no cure for trimethylaminuria, it is possible for people with this condition to live normal, healthy lives. The following are some ways a person with trimethylaminuria can reduce symptoms of odor [3]:

    • Avoiding foods containing trimethylamine and its precursors (choline and trimethylamine-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; brassicas (brussel sprouts, broccoli, cabbage, and cauliflower); and lecithin and lecithin-containing fish oil supplements.  Trimethylamine N-oxide is present in seafood (fish, cephalopods, crustaceans). Freshwater fish have lower levels of trimethylamine N-oxide.
    • Taking low doses of antibiotics to reduce the amount of bacteria in the gut. This suppresses the production of trimethylamine.
    • Taking laxatives can decrease intestinal transit time and reduce the amount of trimethylamine produced in the gut.
    • Taking supplements to decrease the concentration of free trimethylamine in the urine.
    • Activated charcoal taken at a dose of 750mg twice daily for ten days.
    • Copper chlorophyllin taken at a dose of 60mg three times a day after meals for three weeks.
    • Using soaps with a moderate pH, between 5.5 and 6.5. Trimethylamine is a strong base (pH 9.8), thus soaps with pH closer to that of normal skin help retain the secreted trimethylamine in a less volatile form that can be removed by washing.
    • Taking riboflavin (vitamin B2) supplements to enhance any residual FMO3 enzyme activity. Recommended intake is 30-40mg taken 3-5 times per day with food.
    • Avoiding factors that promote sweating, such as exercise, stress, and emotional upsets.

    NOTE: Individuals should follow the treatment advice of their health care 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.

    Choline is essential for nerve and brain development in fetuses and infants, therefore, pregnant and breast-feeding women should consult with their health care provider before restricting their dietary choline.[1]

    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 the condition and to be aware of the risks of passing this disease on to the next generation. Visit the Services section to find a list of online resources that can assist you in finding a genetics clinic near you.

  • Last Reviewed: 2/11/2009

  • Can trimethylaminuria be cured by replacing FMO3, the enzyme, which when absent, is believed to cause the condition? (Back to Top)

  • Unfortunately at this time, enzyme replacement therapy is not an option in the management of trimethylaminuria.[1]
  • Last Reviewed: 2/11/2009


References  (Back)
  1. Learning about Trimethylaminuria. National Human Genome Research Institute Web site. February 3, 2009 Available at: http://www.genome.gov/11508983 . Accessed February 11, 2009.
  2. Trimethylaminuria. Genetics Home Reference Web site. April 2007 Available at: http://ghr.nlm.nih.gov/condition=trimethylaminuria. Accessed February 11, 2009.
  3. Phillips IR, Shephard EA. Trimethylaminuria. GeneReviews Web site. March 18, 2008 Available at: http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=trimethylaminuria. Accessed February 11, 2009.
        • Genetics Home Reference (GHR) contains a condition summary on Trimethylaminuria. Click on the link to go to GHR and review this summary.
        • The Online Mendelian Inheritance in Man (OMIM) database contains genetics resources that discuss Trimethylaminuria. Click on the link to go to OMIM and review these resources.
        • 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.
        • GeneReviews provides a comprehensive review describing the application of genetic testing to the diagnosis, management, and genetic counseling of patients with specific inherited conditions. Click on GeneReviews to view the article on Trimethylaminuria.
        • The United States Department of Agriculture has a document that lists the choline content of common foods. Click on the link above to view this document.
        • Trimethylaminuria Foundation
          P.O. Box 3361
          Grand Central Station
          New York, NY 10163-3361
          Telephone: 212-300-4168
          Fax or alternate phone: 917-640-7308
          E-mail: theTFnetwk@aol.com
          Hours of operation: Tu, Th, Fr until 7 pm and Saturdays until 4 pm
        • Trimethylaminuria Midwest Region Foundation
          12537 Hardy Street
          Overland Park, Kansas 66213
          Contact: Cheryl Fields, MBA
          Telephone: 913-906-9496
          Email: emporia962000@yahoo.com
        • The National Organization of Rare Disorders (NORD) has partnered with Inspire.com to launch an online community for people with rare diseases called The NORD Rare Disease Community. This community connects medical patients, family members, caregivers, and professionals. Click on The NORD Rare Disease Community to learn more.
        • RareShare is an online social hub dedicated to patients, families and healthcare professionals affected by rare medical disorders. Click on RareShare to learn more.
      • There is a study, entitled "Studies of Children with Metabolic and Other Genetic Diseases,'' which is evaluating individuals with known or suspected genetic or metabolic diseases. Despite its title, this study is enrolling individuals of all ages. Since this is a very broad study, individuals with this condition may be eligible to participate. To read about this study online, visit the link above. After you click on the study, review its 'eligibility' criteria to determine its appropriateness.
        • The GeneTests web site lists laboratories performing clinical diagnostic testing. The laboratory testing for TMAU is located in Canada, however, they accept samples from people in the United States. To find out more about this laboratory, click here or select the 'Laboratory Directory' icon at the top the home page. Use 'trimethylaminuria' as your disease search term and click on either the 'Research' or 'Testing' icon for the laboratory's contact information. Again, please note that this laboratory does not accept direct contact from patients; therefore, you will have to work in conjunction with a health care provider or genetics professional. Either of these professionals can contact the laboratory to learn more about the clinical diagnostic testing the laboratory offers for trimethylaminuria.
        • The Human Biomolecular Research Institute can assist in the diagnostic testing of patients who may have trimethylaminuria.


          The Human Biomolecular Research Institute
          5310 Eastgate Mall
          San Diego, CA 92121
          Tel: (858) 458-9305
          Fax: (858) 458-9311
          Email: rhandley@hbri.org
          Web site: http://www.hbri.org/
        • 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.


          Monell Chemical Senses Center
          University of Pennsylvania
          Telephone: (267) 519-4700
          Contact: George Preti, PhD at preti@monell.org
          Web site: http://www.monell.org/tmau_h.htm
        • Laboratory that is able to assist in the diagnostic testing of patients who may have trimethylaminuria. Please note that some laboratories do not accept direct contact from patients. Therefore, we recommend that you work with a medical or genetics professional to contact the laboratories for further information. The Information Center provides the names of these centers for informational purposes only, not as an endorsement of the institutions' products or services.


          Dr. Paul Fennessey (303) 315-7287
          Contact: Dr. Susan Tjoa; (303) 315-8175 or susan.tjoa@uchsc.edu

        • We recommend that you discuss this information and your concerns with a genetics professional. The following online resources can help you find a genetics professional in your community:

           * GeneClinics - A searchable directory of US and international genetics and prenatal diagnosis clinics. To locate genetics clinics in the United States, go to the following link and click on 'Clinic Directory' to find a genetic service close to you. 

            * ResourceLink - A database of genetics counseling services, searchable by location, name, institution, type of practice, or specialty. Hosted by the National Society of Genetic Counselors.

      • The NLM Gateway allows users to search across multiple resources offered on the National Library of Medicine's Web site.  Some of these resources may be duplicated in the list of links above.  Click on the link to go to the NLM Gateway, and search by condition name.

Department of Health & Human Services National Institutes of Health USA.gov - government made easy


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