1,1'-ETHYLIDENEBIS[TRYPTOPHAN] INDUCES PATHOLOGICAL ALTERATIONS IN MUSCLE SIMILAR TO THOSE OBSERVED IN THE EOSINOPHILIA-MYALGIA-SYNDROME

1,1'-Ethylidenebis[tryptophan] (EBT), a derivative of L-tryptophan (LT ), is a trace contaminant in batches of LT implicated by epidemiologic evidence in the pathogenesis of the eosinophilia-myalgia syndrome (EM S). We treated female Lewis rats with EBT or unimplicated LT (4 mg per 100 grams daily) by intraperitoneal injection. No rash or weakness oc curred in either group. All three EBT rats had a few necrotic muscle f ibers. In two rats, perimysium and fascia were abnormally thickened an d infiltrated with lymphocytes, macrophages, and sparse eosinophils; t wo rats had sparse perineurial inflammatory cells. Rats treated with u nimplicated LT showed no abnormality. These findings replicate an impo rtant feature of human EMS and support the epidemiologic evidence link ing EBT to the pathogenesis of the human disease.