Juvenile dermatomyositis: histological findings and pathogenetic hypothesis for the associated skin changes.

Skin biopsies from patients with scleroderma and juvenile dermatomyositis (DM) share many histologic features. Characteristics common to both diseases are particularly evident in the dermal microvasculature and include endothelial swelling and concentric thickening of the vascular basement membrane. Biopsies performed on 3 patients with the severe vasculitic form of juvenile DM showed these changes as well as dropout of vessels and linear deposition of collagen. The latter findings, seen late in the course of the disease, are indistinguishable from those of advanced scleroderma. A hypothesis is presented which attempts to relate these histological findings to a common underlying pathophysiologic mechanism.