Idiopathic Inflammatory Myopathies

Idiopathic inflammatory myopathies (IIMs) are a diverse group of diseases characterized by proximal muscle weakness and inflammation in skeletal muscle. Phenotypically, the subtypes include dermatomyositis, polymyositis, inclusion body myositis, and amyopathic dermatomyositis. The most common IIM in children is juvenile dermatomyositis (JDM). In contrast to adult dermatomyositis (DM), children are likely to have frequent relapses, vasculopathy, and long-term metabolic and other complications like lipodystrophy, insulin resistance, and calcinosis. Significant advances in our understanding of pathogenesis, disease course, and treatment of JDM has changed the therapeutic landscape and improved outcomes in children. Myositis-specific autoantibodies and myositis-associated autoantibodies have unique clinical associations, disease course and help predict response to therapy. A multidisciplinary approach including exercise programs and psychosocial support is essential. The first line of treatment is a combination of corticosteroids and methotrexate (MTX). Other targeted immunosuppressive therapy is used in refractory cases. Early recognition and timely referral to a specialist center remain pivotal to improving the mortality and morbidity associated with this disease.