Trimethylaminuria (TMAU, Fish Odor Syndrome)
What is trimethylaminuria (TMAU)?
Trimethylaminuria (trī-meth'il-am-i-nyūr'ē-ă) (TMAU) is a very rare condition that makes your sweat, breath, saliva and pee smell like rotten fish or rotten eggs. Some people have TMAU due to defective genes passed down from their parents that affect their metabolism. Some illnesses and medications can cause trimethylaminuria. TMAU may not seem like a major health problem, but people who have trimethylaminuria often struggle with psychological and social issues. TMAU can’t be cured. But making changes in your diet, using certain soaps and lotions and managing stress can help reduce its symptoms.
Who’s affected by TMAU?
Trimethylaminuria is very rare, with healthcare providers reporting a few hundred cases in the 30 years they’ve tracked the condition. People assigned female at birth (AFAB) or more likely to have TMAU than people assigned male at birth (AMAB).
Symptoms and Causes
What causes trimethylaminuria?
If you have trimethylaminuria, it means your body can’t process a bad-smelling chemical called trimethylamine. Your intestines produce trimethylamine when you eat some foods, including liver, legumes and eggs.
Normally, your body produces an enzyme called flavin-containing monooxygenase 3 (FMO3). This enzyme breaks down certain chemicals, including trimethlylamine. But when this enzyme doesn’t work, your trimethlylamine levels build up and make your breath, sweat and pee smell bad.
Some people may have trimethylaminuria because they have an inherited metabolic condition that blocks the enzyme from breaking down trimethylamine. Healthcare providers call this primary trimethylaminuria. Primary trimethylaminuria happens when something changes in the FMO3 gene. This gene carries instructions on making the FMO3 enzyme. Without correct instructions, your body can’t make an effective enzyme.
My parents don’t smell bad like I do. Why did I did inherit this condition?
When you inherit genes from your parents, you receive two copies of each gene. If you have primary trimethylaminuria, it means each parent has one copy of a changed FMO3 gene. This changed gene can’t give instructions for making the FMO3 enzyme.
Without that enzyme, your body can’t process the bad-smelling chemical trimethlylamine. But your parents don’t have trimethylaminuria because they both have one normal and one changed gene. They can carry the changed gene, but they won’t have symptoms because this condition requires two changed genes.
Other people develop a form of trimethylaminuria that’s called secondary, acquired or transient trimethylaminuria. In this case, they have FMO3 enzymes, but something prevents the enzyme from completely breaking down trimethylamine. Secondary trimethylaminuria can happen to people who have liver failure or who receive choline supplements to treat Alzheimer’s or Huntington’s disease. Choline is an essential nutrient found in meats, fish, nuts, beans, vegetables and eggs.
What are the signs and symptoms of trimethylaminuria?
People with TMAU give off a strong unpleasant smell that becomes more noticeable after exercise or when they’re under stress. People assigned female at birth (AFAB) may have more severe symptoms just before and during their periods, after taking oral contraceptives and as they go through menopause.
People who inherit trimethylaminuria often struggle with significant psychological and social issues. TMAU symptoms often get worse during puberty, making children vulnerable to being bullied, shunned or ridiculed. Some children with TMAU respond by becoming aggressive and disruptive. Other ways TMAU may affect people’s wellbeing include:
- Avoiding people because they’re embarrassed about their condition. Being socially isolated can lead to depression, frustration and loneliness.
- Having a hard time developing or maintaining relationships.
- Rarely, showing signs of paranoia and suicidal tendencies.
Do people with trimethylaminuria smell themselves?
Yes, just like typical body odor or sweat, people with TMAU may notice how they smell. But like typical body odor or sweat, some people with TMAU may be accustomed to the smell and less likely to react to it than those around them.
I smell like fish after eating fish. Does that mean I have TMAU?
No, but you may have temporary bad breath or fishy-smelly breath after eating fish.
Diagnosis and Tests
How do healthcare providers diagnose trimethylaminuria?
Healthcare providers diagnose TMAU by measuring the amount of trimethylamine in your urine (pee).
Management and Treatment
Can trimethylaminuria be cured?
Primary or inherited trimethylaminuria can’t be cured. But a combination of diet, hygiene and some medications can help make trimethylaminuria symptoms less noticeable.
I have trimethylaminuria. What foods should I avoid?
Healthcare providers may recommend you avoid the following foods:
- Milk from wheat-fed cows.
- Soya products.
- Brussels sprouts.
- Seafood. (You can eat fresh-water fish.)
- Fish oil supplements.
Eliminating these foods may reduce the amount of essential nutrients choline and folate, so ask your healthcare provider about ways to ensure you have enough choline and folate. People with trimethylaminuria who’re pregnant or lactating should not cut back on foods that have choline. If you’re pregnant or lactating, talk to your healthcare provider about other ways you can minimize TMAU symptoms.
What medications treat trimethylaminuria?
Your healthcare provider may prescribe a short course of antibiotics to reduce your gut bacteria so you have less trimethylamine in your gut. They may also recommend probiotics to stimulate gut health and reduce the amount of trimethylaminuria.
What else helps with trimethylaminuria symptoms?
Healthcare providers may recommend using low-pH (acidic) soaps and lotions to reduce odor. They may also suggest ways you can avoid sweating, like changing your exercise routine. Sometimes, stress makes people sweat. Your healthcare provider can recommend ways to manage your stress.
How can I reduce my risk of developing trimethylaminuria?
If you have primary trimethylaminuria, you have an inherited form of the condition that you can’t prevent. Fortunately, changing some personal habits such as diet and hygiene can help reduce your symptoms.
Outlook / Prognosis
What can I expect if I have trimethylaminuria?
TMAU can’t be cured but it can be managed. If you have primary (inherited) trimethylaminuria, changing your diet and some personal habits will make a big difference. If you take medications that cause trimethylaminuria, ask your healthcare provider about alternatives.
You may also benefit from some mental health support. Many people with trimethylaminuria can struggle with social isolation, loneliness, poor self-image and depression.
How do I take care of myself?
You can take care of yourself by thinking of TMAU as something that happened to you. You’re not responsible for your TMAU. But you can take responsibility for managing your symptoms so you can live a full and productive life. Talk to your healthcare provider about ways to manage your diet, exercise and stress so you have less noticeable TMAU symptoms.
What questions should I ask my healthcare provider?
Trimethylaminuria is a very rare condition. Until you were diagnosed, you may not have known it existed. Here are some questions you may want to ask your healthcare provider:
- What is TMAU?
- Why do I have it?
- If I have an inherited form of it, does that mean my children will have it?
- What is the treatment?
- Can you cure it?
- Will I always have these symptoms?
A note from Cleveland Clinic
Some people who have trimethylaminuria go into self-imposed social exile, worried their fishy-smelly symptoms may offend others. Sometimes, people with TMAU believe they still need to keep life at arm’s length even after they know how to reduce their symptoms. If living with TMAU has made you feel isolated, angry, anxious or depressed, you may benefit from some mental health support. If that’s your situation, talk to your healthcare provider. They know what you’ve experienced and can recommend helpful programs and services.
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