Fish Odor Syndrome, Fish Malodor Syndrome, Stale Fish Syndrome
Monday, 21 June 2004
Last Updated Monday, 21 June 2004
What
Trimethylaminuria (TMAU) is a
metabolic disorder in which an individual is missing the
enzyme needed to breakdown a chemical named trimethylamine. Trimethylamine is what makes
FISH smell fishy. This missing
enzyme causes trimethylamine to accumulate in the body and is then released in sweat, urine and breath, giving off a strong fishy odor. Some children with TMAU have a strong odor all the time, but most have a moderate smell that varies in strength over time.
Who
This syndrome seems to be more common in women than men, but the reason for this is not clear. There is some evidence to suggest that female sex hormones, such as progesterone and/or estrogen, aggravate symptoms. The condition is considered rare. Only eighteen cases of the inherited form of TMAU have been reported in the medical literature. However, an accurate count of individuals living with this condition is not available, in part because people with TMAU often show varying degrees of symptoms and thus are not diagnosed.
Signs and Symptoms
Children with TMAU appear normal and healthy. The only symptom they typically have is a fishy odor. In some women, this condition worsens around puberty, just before and during menstrual periods, after taking oral contraceptives, and around menopause. The symptoms can occur at any age and depend on the ingestion of foods that contain trimethylamine. Trimethylamine is produced when
bacteria that are present in the intestine digest proteins. Different types of
bacteria living in the gut also influence how the odor is manifested. It is thought that some types of
bacteria produce more trimethylamine than others, thus increasing symptoms.
In addition, this disorder can have significant social and psychological affects. Many individuals with this disorder are embarrassed or ashamed of the resulting odor and try to conceal the smell rather than seek help. Some parents also think they are not bathing their child enough.
Possible Causes
Trimethylamine is produced as a result of protein digestion. Trimethylamine is produced from the breakdown of certain
amino acids named choline and trimethylamine-oxide. Choline is found in egg yolk, liver, kidney, legumes (soybeans), peas, and some grains. Trimethylamine-oxide is found in some
FISH. The foul odor associated with TMAU is caused when trimethylamine is released into the sweat, breath or urine. Normally the
enzyme monooxygenase 3 (FMO3) breaks down trimethylamine into a compound named trimethylamine-N-oxide that has no odor. Children with TMAU either lack or have an impaired
enzyme.
TMAU is a
genetic disorder, which means it is inherited through genes passed down from one of the parents. TMAU is inherited in an
autosomal dominant fashion; this means only one
gene containing a change from one parent is needed for a person to have this disorder. Most of the mutations that are associated with this disease are on
chromosome 1, where the
gene that codes for the
enzyme FMO3 is located.
It is possible to have a recessive type of TMAU, meaning a
gene containing a change is inherited from both parents. These mutations, or changes, are located on
chromosome 15. There is evidence that people who inherit only one copy of the recessive
gene may have some problems breaking down trimethylamine, though not as much as those who have two copies of the mutated
gene, and therefore may also experience temporary bouts of strong
FISH-odor. This may occur after eating foods that contain large amounts of trimethylamine.
Diagnosis
The only test for TMAU is a urine test for elevated levels of trimethylamine. A similar test can be used to identify carriers of this condition. A
carrier is someone who carries one copy of a mutated
gene but does not have symptoms. In this case, the person would be given a high dose of choline (one of the precursors of trimethylamine) and then have their urine tested for elevated levels of trimethylamine.
Treatment
Although there is no cure for TMAU, it is possible for people with this condition to live normal, healthy lives. Ways of reducing the odor and dealing with the disease include:
avoiding foods containing choline (egg yolk, liver, kidney, soybeans, peas and whole grain wheat) and trimethylamine-oxide (tuna), the precursors of trimethylamine. Taking low doses of antibiotics to reduce the amount of
bacteria in the stomach and intestine can also help. If children are having a difficult time dealing with their disorder, counseling to help with depression and other psychological symptoms is available.
Prognosis
Children with TMAU will have this condition for the rest of their lives. The severity of the odor varies from child to child, and can be managed fairly well. This condition is not known to affect any other organs in the body, and is not life threatening. The lifespan of those with the disease is normal.
Connect with other parents
In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease,
please fill out this brief form.
Weblinks
Online Mendelian Inheritance in Man
http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=602079
An electronic catalog of human genes and genetic disorders, developed by the National Center for Biotechnology Information. The language on this page about Trimethlaminuria is technical, but is considered to be a very comprehensive source of information.
What's That Smell?
http://www.sciencenews.org/pages/sn_arc99/5_15_99/bob2htm
Modern science puts its mark on a rare but ancient body-odor disease. An article about Trimethylaminuria, written by Damaris Christensen, and published by ScienceNewsOnline, Volume 155, Number 20 (May 15, 1999).
http://www.TMAUHelp.com
This site is dedicated to providing information, aid and support for persons afflicted with TMAU.
Online support group for individuals with TMAU
http://health.groups.yahoo.com/group/Trimethylaminuria/
Google Search for Trimethylaminaria
References and Sources
Medline: www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=602079, keyword “trimethylaminuria”
OMIM: www.ncbi.nlm.nih.gov, disease #602079
National Human Genome Research Institute: www.genome.gov/11508983
