L-tryptophan and the eosinophilia-myalgia syndrome: a clinical and laboratory study

Case notes of 202 patients who were prescribed a single brand of L-tryptophan (Optimax, manufactured by Merck) between January 1987 and December 1991 were examined. Fourteen patients' notes indicated that they had clinical or laboratory findings suggestive of a diagnosis of eosinophilia-myalgia syndrome (EMS). However, results of clinical examination and measurement of serum aldolase, total eosinophil count and antinuclear antibodies did not support the diagnosis of EMS in any of the 14 patients. Although a further study of 50 consecutive patients on L-tryptophan at the time of the investigation revealed that 5 had mild eosinophilia, none reached the criteria for EMS established by the US Centers for Disease Control and Prevention.