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L-tryptophan and the eosinophilia-myalgia syndrome


Last October three patients with a previously undescribed syndrome of eosinophilia and severe myalgia were reported in New Mexico. Investigation had excluded other known causes of eosinophilia (e.g. parasitic or fungal infection, allergic disorder, end-stage renal disease or leukaemia) but it was noted that all three patients had been taking supplements of the essential amino acid, L-tryptophan, bought over the counter. Since this was made known to the public and to physicians,1–3 over 1400 cases - mostly in women - have been identified in all parts of the USA, and nineteen deaths have been reported. Two case control studies have confirmed a strong association with use of L-tryptophan-containing preparations4 which have since been recalled from sale in the USA. In Britain, the Chief Medical Officer informed doctors about the syndrome last November.5

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