Childhood dermatomyositis is a connective-tissue disease related to polymyositis, characterized by inflammation of the muscles and the skin. It differs from adult dermatomyositis in several ways, and has two common variants.[1] The more common form is the "Brunsting type," in which slow, progressive muscle weakness with calcinosis can be easily treated with corticosteroids. The second type is known as "Banker type," characterized by a vasculitis of the muscles and gastrointestinal tract, rapid onset of severe weakness, steroid unresponsiveness, and high death date.[1]
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Dermatomyositis is confirmed by proximal muscle weakness, an electromyography with a characteristic "spike and wave" pattern, and abnormal CPK or aldolase levels. Conclusive diagnosis requires a muscle biopsy that shows perifascicular infiltration of inflammatory cells.[2]
The more common type of dermatomyositis, the unicyclic "Brunsting type", responds well to corticosteroids and typically disappears within six months of treatment. Muscular calcifications can be surgically removed, but doing so may result in poor wound healing; calcifications can be reduced with bisphosphonates.[2]
Children with the rare polycyclic form of dermatomyositis can also be treated with corticosteroids and methotrexate, but respond poorly. Muscle cells that die during the inflammatory phase of dermatomyositis are non-renewable, which can lead to permanent weakness.[2]