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.