L-tryptophan induced eosinophilia-myalgia syndrome. We describe the spectrum of clinical and histologic abnormalities of 11 women with L-tryptophan induced eosinophilia-myalgia syndrome. The illness is characterized by musculoskeletal symptoms including myalgias, arthralgias and paresthesias. The physical findings consist of muscle tenderness, neuropathies, rash, peripheral and periorbital edema. Electroneurography performed in 10 patients demonstrated a neuropathy in 5 and myopathic changes in 3. Skin and muscle biopsies showed fascial edema, inflammation and perivascular infiltrates in the skin, whereas perineural infiltrates and venulitis were identified in muscle. Seven patients were treated with prednisone; eosinophilia disappeared promptly although myalgias and neuropathy persisted. 