Bilateral leg pain and unilateral calf atrophy caused by polymyositis accompanying lumbar spinal stenosis and disc herniation: a case report

Polymyositis is a subgroup of idiopathic inflammatory myopathies characterized by symmetric proximal limb weakness and chronic skeletal muscle inflammation. We herein report the first case of bilateral leg pain and unilateral calf atrophy caused by polymyositis accompanying lumbar spinal stenosis and disc herniation. A 52-year-old man presented with intermittent claudication and calf pain that had become gradually aggravated during the last 3 months. Magnetic resonance imaging showed spinal stenosis at the L3/4 and L4/5 levels and lumbar disc herniation at the L4/5 level. Preoperative laboratory investigations revealed elevated muscle enzyme concentrations. Magnetic resonance imaging also showed atrophy, fatty degeneration, and edema in both calf muscles. Histological examination showed inflammatory myositis and fibrosis in the perifascicular connective tissues. The patient was diagnosed with polymyositis. We performed decompressive laminectomy at the L3/4 and L4/5 levels and discectomy at the L4/5 level. After administration of prednisolone for 6 months and methotrexate for 3 months, the patient's bilateral calf pain and abnormal laboratory findings improved. The combination of surgical decompression and adequate medical treatment resulted in a successful recovery. Polymyositis should be suspected in patients with lumbar spinal stenosis or lumbar disc herniation who exhibit increased muscle enzyme concentrations or lower extremity muscle atrophy.