DIAGNOSIS OF A NEW CASE OF TRIMETHYLAMINURIA USING DIRECT PROTON NMR-SPECTROSCOPY OF URINE

Trimethylaminuria (TMA-uria; McKusick 275700) is the characteristic biochemical abnormality leading to the so-called fish odour syndrome, a distressing condition of body malodour causing serious psychosocial problems (Ayesh et al 1993). TMA is mainly derived from bacterial degradation of dietary quaternary amines such as choline, lecithine and carnitine in the gut. TMA-uria is thought to result from overproduction and/or defective N-oxidation of TMA. To differentiate between the two possible causes of TMA-uria, one should be able to measure both TMA and its N-oxide TMAO. The N-oxidation defect, presumably due to a deficient liver TMA-N-oxidase, is inherited in an autosomal recessive fashion. TMA is usually assayed by either gas chromatography (GC) or GC-mass spectrometry (Tjoa and Fennessey 1991). For this purpose TMA has to be recovered from the urine by purging and trapping. TMAO can only be measured after reduction to TMA. We now report the application of a simple and direct method based on proton NMR spectroscopy.