Recently, Casado et al3 performed the first prospective study of AMM. Screening their patients' muscle enzyme levels, including creatine kinase, lactate dehydrogenase, and aldolase, the authors further evaluated those having persistently elevated levels of muscle enzymes with physical examination, electromyography, and muscle biopsy. Of 119 patients screened, 22 (18.5%) had persistently elevated muscle enzyme levels, and excluding 7 patients lost to follow-up, the remaining 15 patients (12.6%) all demonstrated characteristic curvilinear and/or myeloid bodies on skeletal muscle electron microscopy (defined as AMM). However, only 8 of these patients (6.7%) manifested clinical muscle weakness (defined as clinical AMM), which improved in all patients on cessation of antimalarial therapy. Casado et al3 report the prevalence of AMM (12.6%) and clinical AMM (6.7%) as higher than that previously reported (<2%), and they suggest screening patients without clinical symptoms by measuring muscle enzymes on a repeated basis.