Inflammatory myopathies: management of steroid resistance

The inflammatory myopathies include polymyositis, dermatomyositis, necrotizing autoimmune myopathy (NAM), and inclusion body myositis (IBM). On the basis of clinical experience, most patients respond to corticosterioids to some degree or for a time period. For patients insufficiently responding or for steroid-sparing, the treatment options vary among practitioners, generating a genuine uncertainty. This timely review highlights emerging new therapies and provides practical therapeutic algorithms.

For patients insufficiently responding to corticosteroids, the commonly used immunosuppressants, such as azathioprine, mycophenolate, methotrexate, or cyclosporine, may exert a nonevidence-based 'steroid-sparing' effect but provide minimal benefit on their own. The second line therapy is intravenous immunoglobulin (IVIg) based on a controlled study conducted in dermatomyositis; the drug is also effective in many patients with polymyositis and NAM. Rituximab and tacrolimus may offer additional benefit. Anti-TNF agents are disappointing. IBM remains difficult to treat; although early on some patients may partially respond to steroids or IVIg, they soon become unresponsive and the disease progresses. Emerging agents against T cells, B cells, and transmigration molecules are discussed as promising therapeutic options.

New biological agents are in the offing for control trials. Appropriate outcome measures are however needed to assess and monitor responses.