Trimethylaminuria (TMAU)
Description
Trimethylaminuria (TMAU), also known as ‘fish odor syndrome,‘ is a rare metabolic disorder that affects an individual‘s ability to break down trimethylamine, a compound that contributes to a strong fishy body odor. This condition is often inherited and can cause significant social and psychological distress for those affected. This blog will explore the causes, symptoms, diagnosis, and management of TMAU, empowering you to understand this disorder and find ways to thrive despite its challenges.
Genes Involved
The genes involved in TMAU are primarily responsible for producing enzymes that break down trimethylamine. These genes include:
- FMO3 (Flavin-containing monooxygenase 3): This gene is most commonly associated with TMAU and encodes the enzyme FMO3, which plays a crucial role in oxidizing trimethylamine into a less odorous compound.
- Other genes: While less common, mutations in other genes involved in trimethylamine metabolism, such as the aldehyde dehydrogenase 2 (ALDH2) gene, can also contribute to TMAU.
Recognizing the Signs and Symptoms
The most prominent symptom of TMAU is a strong, persistent fishy odor emanating from the body, particularly noticeable in sweat, urine, and breath. This odor can be intensified after consuming certain foods like fish, eggs, legumes, and red meat. Other potential symptoms include:
- Headaches
- Nausea
- Gastrointestinal discomfort
- Skin irritation
- Psychological distress and social anxiety
Causes
TMAU is mainly caused by genetic mutations that affect the function of the enzyme FMO3. This enzyme is responsible for converting trimethylamine, a compound produced by the breakdown of certain foods, into a less odorous compound. When FMO3 activity is impaired, trimethylamine accumulates in the body and is released through sweat, urine, and breath, causing the characteristic fishy odor.
In some cases, TMAU may also be caused by factors other than genetic mutations, such as:
- Dietary factors: Consuming foods high in trimethylamine precursors, such as fish, eggs, legumes, and red meat, can exacerbate the fishy odor.
- Gut bacteria: The composition of gut bacteria can also influence trimethylamine production.
- Liver disease: Liver dysfunction can impair the body‘s ability to process trimethylamine.
Inheritance/recurrence risk
TMAU is typically an autosomal recessive disorder, meaning both parents must carry the mutated gene for their child to inherit the condition. If both parents are carriers, there is a 25% chance their child will inherit TMAU, a 50% chance of being a carrier, and a 25% chance of not inheriting the mutation. However, in some cases, TMAU can also be caused by spontaneous mutations, occurring without a family history of the disorder.
