Juvenile Dermatomyositis

Published on 06/06/2015 by admin

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Last modified 06/06/2015

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27 Juvenile Dermatomyositis

Juvenile dermatomyositis (JDMS) is the most common inflammatory myositis during childhood, accounting for more than 80% of cases. Endothelial injury of the capillaries, venules, and small arteries of the muscle, skin, and gastrointestinal tract characterize JDMS. It is a distinct disease from adult-onset dermatomyositis because it is not associated with malignancy and tends to remit after several years.

Clinical Presentation

JDMS is a rare inflammatory myopathy with an incidence of two to four cases per million per year in children ages 16 years and younger. The mean age of onset is 7 years. However, there is a bimodal distribution with peaks at 2 to 5 years and 12 to 13 years. It is more common in girls than boys by a ratio of 2 : 1. There is no racial predominance.

Cutaneous Features

Dermatomyositis has several classic cutaneous findings (Figure 27-1). Gottron’s papules are erythematous, raised, scaling plaques on the dorsal surface of the knuckles, elbows, and knees that are present in more than 90% of children at the time of diagnosis. Gottron’s papules are frequently confused with severe eczema if JDMS is not suspected. The classic heliotrope rash is a violaceous discoloration of the eyelids with associated eyelid edema; this is present in approximately 80% of children at diagnosis. About 40% of children also have a prominent erythematous malar rash. This rash can be ulcerative, cross the nasolabial folds, and extend onto the forehead. Raynaud’s phenomenon (Figure 27-2) and associated nailfold capillary changes are seen in up to 80% of patients. Nailfold changes are characterized by proximal nailfold erythema, capillary dilatation, tortuosity, or dropout. The measured density of capillaries per millimeter may be a useful tool for monitoring clinical activity. Skin ulcerations reflect significant vasculopathy of the skin and may be a sign of internal organ vasculopathy. Ulcerative skin lesions are associated with more severe disease and worse prognosis.

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