FISH ODOR SYNDROME (TRIMETHYLAMINURIA)
Fish odor syndrome is a rare condition in which the body’s metabolic processes fail to break down the chemical compound trimethylamine, notable for its pungent odor.
- Trimethylamine has been described as an unpleasant strong fishy smelling compound.
- When the normal metabolic process fails, trimethylamine accumulates in the body and is excreted in the urine, sweat, and breath.
- The intensity of the odor may vary over time.
- The condition is more prevalent in women than in men.
- The consequences of emitting a foul odor can be socially and psychologically damaging as it can interfere with many aspects of daily life’s affecting a person’s relationships, social life, and career, leading to other problems such as depression and isolation.
CAUSES
Fish odor syndrome is caused by mutations in the FMO3 gene. This gene provides instruction for an enzyme that breaks down nitrogen-containing compounds from diets, including trimethylamine. Trimethylamine is produced by bacteria in the mammalian gut during digestion of proteins from eggs, liver, legumes (soybeans and peas), certain kind of fish, and other foods. Normally, the fishy-smelling trimethylamine is converted into trimethylamine N-oxide which has no odor. If the enzyme is missing or its activity is reduced as a result of a mutation in the FMO3 gene, trimethylamine is not processed properly and can build up in the body causing the odor associated with the condition. Experts believe that stress and diet can play a large role in triggering symptoms.
Most cases of fish odor syndrome appear to be inherited in an autosomal recessive pattern, which means that a person inherits two mutated genes, one from each parent. Most often, the parents of an individual with an autosomal recessive condition are each carrier of the mutated gene, meaning that each parent carries one copy of the mutated gene. Carriers of an FMO3 mutation may have mild symptoms or experience temporary episodes of strong body odor.
A secondary form of fish odor syndrome may exist where there is no genetic cause, yet excessive trimethylamine is secreted due to hormonal causes, an abnormal increase of bacteria that produce trimethylamine, or an excess of certain protein in diets. A few cases have been identified in adults with kidney or liver disease.
SYMPTOMS
Symptoms can be from birth or start later in life, often around puberty.
The only symptoms associated with the condition is an unpleasant smell, typically of rotten fish that can affect urine, vaginal fluids, sweat, breath.
In women, symptoms may worsen just before and during menstrual periods, around menopause, and after taking oral contraceptives.
DIAGNOSIS AND TREATMENT
Diagnosis of the condition is based on a urinary analysis of trimethylamine and trimethylamine N-oxide. The doctor will measure the ratio of trimethylamine to trimethylamine oxide in the urine. This can help to distinguish between mild and severe cases.
A blood test may also be carried out to provide genetic analysis. This will help to distinguish between primary genetic trimethylaminuria from the secondary non-genetic form of the condition.
TREATMENT
No known cure or treatment exists for the condition, but symptoms can be improved by making certain lifestyle changes, and if possible certain medications. This may include:
- Avoiding foods such as egg yolks, red meats, beans, legumes, liver and kidney, and other foods containing lecithin, sulfur, choline, and nitrogen.
- Taking low doses of gut-sterilizing antibiotics such as metronidazole to reduce the number of bacteria.
- Washing the skin with slightly acidic soap with a pH of 5.5 to 6.5