ABSTRACT
DEFINITION Juvenile dermatomyositis (JDM) is an inflammatory vasculopathy that affects primarily the skin and the skeletal muscles. JDM represents 20% of all inflammatory myositis and is the most common inflammatory myopathy in children. Classic findings are Gottron rash and papules, heliotrope rash, calcinosis cutis, and symmetric, proximal muscle weakness. Diagnosis is made by Bohan and Peter (1975a): a characteristic rash, proximal muscle weakness, elevated muscle enzymes, EMG results of polyphasic, low-amplitude motor unit potentials with insertional irritability and fibrillations, and muscle biopsy with inflammation and/or vasculitis. Skin findings with three other features are necessary to make the diagnosis (Table 19).
