Treatment of dermatomyositis and polymyositis

Since idiopathic inflammatory myositis is relatively uncommon, randomized placebo controlled trials are rare. Although corticosteroids have not been tested in randomized controlled trials, general clinical consensus among physicians has accepted it as effective therapy. However, corticosteroid toxicity leads to significant disability in many patients. For patients with refractory dermatomyositis, intravenous immunoglobulin is an effective short-term treatment but its long-term effect remains unknown. Immunosuppressants are commonly used in refractory inflammatory myositis; evidence for their efficacy, with very few exceptions, has been derived from case reports and open studies with small numbers of patients. Even in randomized trials, the lack of validated and generally accepted outcome measures makes it difficult to compare the effect of interventions in different studies. Although the balance of evidence suggests that immunosuppressants are equally effective in dermatomyositis and polymyositis, there are no randomized controlled trials to show if any of these drugs, individually or in combination, is best. For uncommon diseases, such as inflammatory myositis, only multicentre randomized controlled trials involving rheumatologists and neurologists will define the optimal therapy.