RESUMEN
Objective To explore clinical and muscular pathological features of statin-induced myopathy.Methods Nine patients were enrolled in this study,who were diagnosed as statin-induced myopathy by muscle biopsy in Peking University First Hospital from April,2012 to October,2014.The clinical data and pathological findings were analyzed.Results The exposure time to statins varied from 4 days to 4 years in the total of 9 patients,6 males and 3 females,with the average age of 63 ± 6 (55 to 74) years old.Three patients suffered from myalgia and 6 patients complained of weakness mainly at the proximal limbs,while no symptoms occured in 3 patients.Serum creatine kinase (CK) increased in all patients with the maximum value varied from 468 to 8 000 U/L.Serum myositis antibodies were tested in 7 patients and all were negative.Electromyogram was performed in six patients with myogenic damage found in 2 patients.MRI of bilateral thigh muscle was carried out in six patients with muscle edema and mild fatty infiltration found in 2 patients.All patients underwent skeletal muscle biopsy with histochemical and immunohistochemical staining.The main muscular pathological features were muscle fiber atrophy,necrosis,regeneration and increased lipid droplets.Ragged blue fiber,cytochrome C oxidase-negative muscle fibers and decreased NADH activity were observed in some patients.MHC-Ⅰ expressed in the sarcolemma of muscle fibers at various levels.Mild C5b-9 staining was found in the endomysium,capillary and cytoplasm.Symptoms and the level of CK were improved in 7 patients after discontinuing statins or changing to another statin,while the immunosuppressive therapy were used in 2 patients and shown to be effective.Conclusions Statin induced myopathy is self-limiting in most patients,with improvement after discontinuation of statins.Few patients with autoimmune necrotic myopathy need immunosuppressive therapy.