Ability to detect malodour might be genetic.

EDITOR,-In their study of subjects suffering from trimethylaminuria R Ayesh and colleagues observed that six of the 11 patients were unaware of their malodour.1 I report a small controlled study of the ability of normal, healthy subjects to detect the odour of trimethylamine. A mother complained that her 6 year old daughter had an unpleasant smell, which was present most of the time but was worse during hot weather and in the mornings. The problem was so severe that she showered the girl and changed her clothing several times a day. There was no history of incontinence of urine or faeces, and she was otherwise asymptomatic. The girl had three siblings, and neither they nor the parents suffered from malodour. Physical examination yielded un-remarkable findings, and no unpleasant smell was detected by any of the three doctors who examined her at various intervals, although on at least one of these occasions the mother said that the smell was present. Results of analysis of urine and of screening for urinary organic and amino acids were normal, but raised urinary trimethylamine excretion was detected by mass spectrometry (G Thompson, Royal Children's Hospital, Melbourne, Australia). She was started on a diet low in choline and free of fish, with modest effect. Samples of early morning urine from the patient and her asymptomatic sister were presented in unmarked containers for olfactory testing at a departmental meeting. None of the nine participants complained of rhinitis, coryza, or anosmia. Three of the subjects were unable to detect any odour in either specimen; of the remaining six, all could detect an unpleasant smell in the urine from the affected patient and none in the control urine. Lison et al observed that the ability to detect the unpleasant smell resulting from the excretion of metabolites of asparagus in urine is genetically determined and has a bimodal distribution.2 I speculate that the same may be true of the ability to detect trimethylamine in urine. I therefore advise caution in dismissing a complaint that a person suffers from malodour simply because you cannot detect the smell yourself. injury EDr1OR,-Douglas Gentleman and colleagues emphasise the importance of resuscitation in the management of severe head injury.' A paper from the traumatic coma data bank published earlier this year studied 699 cases of severe head injury and showed that initial systemic hypotension was associated with a 150% increase in mortality.2 This suggests that …