Juvenile dermatomyositis

Juvenile dermatomyositis (JDM) is a chronic multisystem inflammatory disease that primarily involves skin and muscles. The clinical picture is mainly characterized by the typical cutaneous rash and by skeletal muscle weakness. Nevertheless the vasculitic process may extend in some cases to other organs such as lung, joints or gastrointestinal system. Calcinosis represents a relatively frequent complication of JDM and occurs in most cases during the late stage of the disease. Usually serum levels of muscle enzymes are elevated and electromyography shows signs of myositis. Muscle biopsy is generally performed only in doubtful cases. JDM should be differentiated from the muscle involvement of other diffuse inflammatory connective tissue diseases and from non inflammatory myopathies. The treatment is mainly based on steroids, whose dosage and regimen depend on disease severity. Steroid therapy has greatly improved the prognosis of JDM.