Eosinophilia-myalgia syndrome: coming to grips with a new illness

In late October 1989, over 1,500 cases of an unusual illness involving severe myalgia and striking peripheral eosinophilia were reported in the United States and several other countries. Other clinical manifestations included pulmonary involvement (interstitial infiltrates and pleural effusions), skin rash and edema, axonal polyneuropathy, perimyositis, and possible adverse neurocognitive effects. Because of the primary manifestations of the illness, it was named "eosinophilia-myalgia syndrome" (EMS) by the Centers for Disease Control. Epidemiologic studies clearly linked illness to the ingestion of tryptophan produced by a single manufacturer in Japan, and the time course of the epidemic was most consistent with its being caused by a product contaminant. Epidemiologic analysis of plant operating conditions and data obtained from chemical analyses of case- and control-associated lots implicated 1,1'-ethylidene-bis(tryptophan) (EBT) as a candidate for the compound that causes EMS. However, the etiologic significance of EBT is still uncertain. Factors found to increase a person's risk for EMS included higher tryptophan dose and older age. Although cases occurred predominantly in women and patients had frequently been taking other medications concurrently with tryptophan, sex and use of several categories of other medications were not shown to influence the risk of illness. Few patients recovered rapidly and fully from the disease. Many were treated with glucocorticoid medications, and although they may have benefited from therapy in the short term, the development of chronic sequelae of EMS appears not to have been prevented. Public health practitioners currently depend on the reports of alert clinicians to detect this type of outbreak. In this case, state and federal government epidemiologists, once they were notified, were able to develop substantial basic information about the epidemic in a relatively short time. Control measures were introduced rapidly, effectively stopping the epidemic.