Polymyositis and dermatomyositis are autoimmune inflammatory myopathies characterized by muscle weakness and inflammation. Current recommended therapy includes corticosteroids as mainstay treatment in addition to immunosuppressant. We present herein a 25year-old female with dermatomyositis and cardiac involvement resistant to disease modifying anti-rheumatic drugs and anti-tumor necrosis factor-alpha. She was treated with anti-CD20 monoclonal antibody, rituximab. The patient demonstrated a remarkable clinical and laboratory response. B-cell depletion therapy with rituximab may be a viable option in patients with dermatomyositis and heart disease.