Eosinophilia-myalgia syndrome. A clinical case series of 21 patients. New Mexico Eosinophilia-Myalgia Syndrome Study Group. We reviewed 21 cases of eosinophilia-myalgia syndrome to describe the range of clinical findings in these patients. Most patients were women (20 [95%]) and middle-aged (mean, 46 years) and had taken the food supplement L-tryptophan (95%). All cases involved eosinophilia (eosinophil count, greater than or equal to 2.0 x 10(9)/L) and incapacitating myalgias. Fourteen (88%) of the 16 patients tested had mild liver function abnormalities. Aldolase levels were abnormal in all patients tested. Muscle biopsies were done in five patients; four showed eosinophilic perimyositis, and one had interstitial inflammation. No physical finding was pathognomonic or universal, but muscle tenderness, tachycardia, and rash were the most common signs found during physical examinations. Seven patients were treated with prednisone, and six showed improvement in muscle pain and a decrease in eosinophilia. The cause of this disorder is still unknown. 