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|Year : 2013 | Volume
| Issue : 3 | Page : 236-237
The fish malodor syndrome: A new indication for gastric bypass surgery?
R Hussain1, K Shipman2, A Haddon1, M Labib1
1 Department of Chemical Pathology, Weight Management Clinic, Dudley Group NHS Foundation Trust, Russells Hall Hospital, Dudley, West Midlands, United Kingdom
2 Department of Clinical Biochemistry, Weight Management Clinic, Dudley Group NHS Foundation Trust, Russells Hall Hospital, Dudley, West Midlands, United Kingdom
|Date of Web Publication||12-Sep-2013|
Department of Clinical Biochemistry, Weight Management Clinic, Dudley Group NHS Foundation Trust, Russells Hall Hospital, Dudley, West Midlands
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Hussain R, Shipman K, Haddon A, Labib M. The fish malodor syndrome: A new indication for gastric bypass surgery?. J Postgrad Med 2013;59:236-7
In 2007, a 41-year-old female was referred to the weight management clinic for consideration of bariatric surgery. She had a body mass index (BMI) of 47.2 kg/m 2 and her comorbidities included hypertension and dyslipidemia. During an initial consultation, she described a long-standing problem with body odor. She complained of a fish odor affecting her sweat and breath, which worsened during menstruation. Fish malodor syndrome or trimethylaminuria was suspected and further investigations revealed raised urinary free trimethylamine (TMA) and TMA/TMA-n-oxide ratio confirming the diagnosis [Table 1]. Full sequencing of the flavin monooxygenase 3 gene (FMO3) found no mutation suggesting that her trimethylaminuria was unlikely to be primary. A low choline diet was recommended and she was treated with a 7-day course of oral metronidazole for possible intestinal bacterial overproduction; however, urine TMA and TMA/TMA-n-oxide ratios continued to remain elevated [Table 1]. In May 2009, she was advised to go on a strict low choline diet and by July 2009 she reported some improvement in her symptoms, which was associated with a reduction of her urinary TMA level.
|Table 1: Urinary TMA, TMA‑n‑oxide and TMA/TMA‑n‑oxide ratio in response to antibiotic (metronidazole), low choline diet and gastric bypass surgery|
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In July 2010, she underwent laparoscopic Roux-en-Y gastric bypass surgery for her obesity. She was advised to continue the low choline diet, but admitted to relaxing her diet following the surgery as it was too restrictive. Eighteen months following surgery, she had lost 56.9% of her excess body weight achieving a BMI of 37.2 kg/m 2 . She also reported a dramatic improvement in body odor and her urinary TMA and TMA/TMA-n-oxide ratio were substantially reduced [Table 1].
Trimethylaminuria or Fish malodor syndrome is an uncommon condition, which results in accumulation of TMA causing the person to smell like rotting fish. , TMA is derived by bacterial metabolism of dietary precursors [Table 2] in the small intestine and is converted into an odorless compound, TMA-n-oxide, by the flavin monooxygenase enzyme FMO3 in the liver.  In excess of 25 mutations have been located in the FMO3 gene and some of these mutations are associated with reduced enzyme activity (primary trimethylaminuria). In secondary or acquired trimethylaminuria, the supply of substrate exceeds the ability of FMO3 to metabolize it, resulting in excessive amounts of TMA being excreted in sweat, urine, breath, saliva and vaginal secretions.  Increased TMA supply can occur in bacterial overgrowth and liver disease can impair metabolism.  The condition can be very distressing for the patient resulting in severe depression and occasionally, suicidal tendencies. The use of soaps, antibiotics and low choline diets may be effective and are the current first-line treatments. 
|Table 2: Major food sources of TMA and its precursors (choline and carnitine)|
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To our knowledge, this is the first report of improvement in trimethylaminuria as a result of Roux-en-Y gastric bypass surgery. We postulate that the improvement in our patient could have been due to several possible mechanisms: a reduction in the quantity of the precursor as a result of an overall reduction in food consumption; a change in bowel flora due to formation of a blind loop  reduced bacterial overproduction; the malabsorption of bile,  which is rich in choline; or a combination of these mechanims. With an increasing number of patients being identified with the fish malodor syndrome,  we suggest that in those morbidly obese, and in whom conservative measures have failed, gastric bypass surgery may likely provide a new approach for the management for this very distressing condition.
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[Table 1], [Table 2]