Juvenile Dermatomyositis and Other Inflammatory Myopathies in Children

Juvenile idiopathic inflammatory myopathy (JIIM) is heterogeneous in presentation, response to therapy, and outcome, despite this not applying to muscle inflammation and dysfunction. The characteristic rash, a component of several types of myopathies, is related more to microvascular damage than to muscle inflammation. The recent observation that myositis specific antibodies are associated with specific patterns of symptoms and outcome is a major advance in classification and may assist in dissecting their distinct disease pathophysiology. The most common JIIM is juvenile dermatomyositis (JDM), accounting for 85% of cases, while, in contrast to adults, juvenile polymyositis is rarely seen. This chapter's goal is to acquaint the reader with physical and laboratory data in children with JDM/other JIIM and to provide guidelines for evaluation and therapy. Our current understanding of pathophysiology is presented; it is expected that new mechanisms of disease will be identified, directing the development of more specific therapies than the general immunosuppression currently in use.