In view of the patient describing his urine as having a fishy smell: Fish-odor syndrome was suspected as the likely cause. To confirm this, a 24-h urine specimen was sent for trimethylamine analysis. Results showed raised levels and raised trimethylamine/trimethylamine-N-oxide ratio.
Primary/inherited trimethylaminuria is most commonly due to an autosomal-recessive mutation in the FMO3 gene. Secondary trimethylaminuria is due to bacterial overgrowth. A low-choline diet and cofactor riboflavin is used to treat fish-odor syndrome. Transient trimethylaminuria may also respond to antibiotic treatment. In our patient, treatment resulted in complete resolution of his symptoms.