Diagnostic value of MRI in inflammatory myositis

A 65-year-old woman presented with a 5-week history of generalized weakness and myalgia. She had a history of seropositive myasthenia gravis post thymectomy for invasive thymoma and was in pharmacologic remission on prednisone and methotrexate. Although limited by significant pain, examination showed diffuse proximal and distal weakness. Serum creatine kinase (CK) was 572 IU/L. Myositis antibody panel was negative. MRI of her left extremities showed patchy muscle edema and inflammation (figures 1 and 2). Given the history of myasthenia gravis and thymoma, diagnosis of granulomatous myositis was made. Increased doses of prednisone and methotrexate resulted in resolution of pain and weakness and normalization of CK levels (51 IU/L).