Trimethylaminuria

Abstract

Trimethylaminuria or fish odour syndrome (OMIM 602079) is characterised clinically by an offensive fish-like smell or better malodour often in childhood. The severity of the syndrome is highly variable. A dietary therapy strategy is known. The fish odour syndrome is caused by defects in the FMO3 gene that encodes a flavin containing mono-oxygenase in liver. In the deficiency state one of the enzyme's substrates trimethylamine (= TMA) will not be adequately converted to TMA N-oxide. The TMA has a pungent odour of rotting fish thus causing the problems. To diagnose a patient with this defect analytical techniques are available that quantify TMA and its N-oxide. These are proton NMR spectroscopy, head space gas chromatography or head space mass spectrometry. In some patients a loading test is required to find indications for this diagnosis at the metabolite level. This chapter describes the available techniques as well as the various forms of the loading test that have been used in literature. © 2008 Springer-Verlag.