Paper: Transient trimethylaminuria in childhood, not because of poor enzyme function : 1998 Paper

This 1998 paper reports on two unrelated and otherwise healthy children with transient trimethylaminuria, a hitherto unknown abnormality, without N-oxidation deficiency. This demonstrates that a diagnosis of fish-odour syndrome should include the analysis of urinary excretion not only of trimethylamine but also of trimethylamine-N-oxide (TMAO).

http://www.ncbi.nlm.nih.gov/pubmed/9846928
Mayatepek E, Kohlmüller D
Children's Hospital, Heidelberg, Germany

Comment from the author who is a sufferer, not an expert:

There are 2 points of interest regarding this study. One is that it is now suggested that FMO1 is the most common form of the FMO enzyme in the human fetus. FMO3 then starts to express itself after birth, but can take quite a few years to fully develop. Around 9 or even teen years has been mentioned. FMO3 is the dominant FMO enzyme in humans after birth.

The other is that the paper suggests tma-n-oxide should be tested. Perhaps up until then, only tma levels were checked. Now 'primary TMAU' diagnosis seems to be based upon the levels of tma-n-oxide a person produces, since this is the correct finished metabolite. It may also explain why in the UK, they accept a diagnosis of 'Secondary TMAU', where the result is given because of too much TMA in the urine. In the case of the paper, today that would be regarded as Secondary TMAU cases (i.e. too much trimethylamine).