Treatment of inflammatory myopathies

Although there have been considerable advances in our understanding of the immunopathogenesis of the different forms of autoimmune inflammatory myopathy, the treatment of these conditions remains largely empirical, being based upon the use of immunosuppressive and immunomodulatory therapies which, for the most part, are non-selective in their actions. Corticosteroids are usually effective in adult and childhood cases of polymyositis and dermatomyositis, but are only rarely helpful in inclusion body myositis, which is usually also unresponsive to other forms of immunosuppressive therapy. Alternate-day corticosteroid therapy has a role in patients with mild disease and as a means of minimizing the side-effects of steroids. This may also be achieved by the early introduction of a second-line agent such as methotrexate or azathioprine, which will allow more rapid steroid withdrawal and may also improve the chances of inducing a remission in more severe cases. In patients who fail to respond adequately to oral corticosteroids, or who relapse after an initial response, intravenous immunoglobulin therapy or pulse therapy with intravenous methylprednisolone are promising approaches which appeal as safer alternatives to cytotoxic drugs. However these forms of treatment will require further evaluation in prospective clinical trials. The same applies to cyclosporin, which has a more selective action on T cells, and which has been reported to be effective in resistant cases of adult and juvenile polymyositis and dermatomyositis. In the longer term, the development of more specific forms of immunotherapy for these myopathies, aimed at blocking autoantigen presentation or its interaction with T cells, awaits the identification of the target antigens and T cells which initiate the autoimmune process.