Drugs in induction and treatment of idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIM) are a rare disease; so far standardized therapy has not been adequately defined by national or international guidelines or recommendations. Corticosteroids are the mainstay of treatment, but these drugs are burdened by several side effects. Thus, additional treatment based on immunosuppressive agents, especially azathioprine, methotrexate, mycophenolate mofetil and cyclosporine, is often needed. This combinate approach both improves the disease response and allows reduction of the dosage of corticosteroids, decreasing the risk of steroid-related long-term complications. Biological agents, particularly B cell depleting agent, are emergent therapeutic tools for refractory cases. Notably, drugs currently used for the therapy of IIM or other rheumatologic and non-rheumatologic conditions can induce myopathy. Drug-induced myopathies represent a considerable part of the complex topic of muscular disorders and should be always considered in the usual diagnostic work-up of a subject with muscle disease. Several mechanisms have been advocated to explain muscular damage induced by a number of drugs and, although a recovery after drug removal is usually observed, severe or persistent myopathy may be observed following the administration of some drugs, particularly in subjects with genetic predisposition. In this review the traditional and novel therapeutic approaches for patients with IIM, particularly biologics, will be discussed and an overview on drug-induced myopathies will also be provided.