Inflammatory myopathies

Abstract

The mainstay of treatment for the idiopathic inflammatory myopathies currently and traditionally has been therapeutics aimed at suppressing or modifying the immune system. Most therapies being used are directed towards polymyositis (PM) and dermatomyositis (DM), as there is yet to be efficacious treatment of any kind for inclusion body myositis (IBM), However, there are few randomized controlled studies supporting the use of such therapies even in PM and DM. Even in the absence of controlled studies, oral corticosteroids (in particular high-dose prednisone) continue to be the first-line medications used to manage these conditions. Second-line therapies include the addition of chronic, steroid-sparing immunosuppressive drugs such as azathioprine, methotrexate, cyclosporine, cyclophosphamide, and mycophenolate mofetil. These drugs are typically added when patients are on corticosteroids for an extended period or when the disease is refractory. Such medications often allow corticosteroid dosages to be reduced, but monitoring is required for their own side effects, such as bone marrow suppression, kidney dysfunction, and respiratory concerns. Small controlled studies also support the role of intravenous immunoglobulin therapy as an alternative therapy, particularly for DM, though the cost of this treatment is sometimes prohibitive. Rituximab, a monoclonal antibody that depletes B cells, has also shown efficacy in uncontrolled studies in DM and holds promise for the treatment of this disease. Other promising immunotherapies currently under study are inhibitors of interferon-α and tumor necrosis factor-α. Unfortunately, though a number of immunomodulatory treatments have been investigated in IBM, none has convincingly demonstrated benefit.