Idiopathic inflammatory myopathy

The idiopathic inflammatory myopathies, especially dermatomyositis and polymyositis, are systemic autoimmune diseases with significant mortality and morbidity. Muscle weakness of the proximal muscles is the most common presenting clinical feature. Since idiopathic inflammatory myopathy is relatively uncommon, randomized control trials are scarce, and no evidence-based optimal treatment regimen has been defined. Corticosteroids are first-line treatment but many patients will require further immunosuppressive or immunomodulatory treatment. Methotrexate, azathioprine and mycophenolate mofetil are among the most commonly used second-line agents, although their benefit has not been adequately studied in randomized control trials. In dermatomyositis, one randomized controlled trial showed that intravenous immunoglobulin is effective. More recently, mycophenolate mofetil and rituximab have shown therapeutic promise, but a small clinical trial of infliximab failed to demonstrate clinical effectiveness.