Contaminants in L-Tryptophan associated with eosinophilia myalgia syndrome

In late 1989, an epidemic of eosinophilia-myalgia syndrome (EMS) that resulted in several thousand cases of the syndrome and 36 deaths was recognized in the United States. Physicians in New Mexico linked the epidemic to the ingestion of L-tryptophan (LT). Results of studies indicated that one or more trace contaminants in LT were likely causes of the EMS epidemic. Investigators traced the LT that was taken by most patients with EMS to a single manufacturer, Showa Denko K.K. of Japan.