An electron microscopic study of childhood dermatomyositis

Muscle biopsies from 12 patients with a typical clinical picture of dermatomyositis have been examined by electron microscopy. Endothelial cells of intramuscular blood vessels, their basal lamina, pericytes, muscle fibers, and satellite cells show degenerative or regenerative alterations. In nine patients, tubular arrays were noted in the cisterns of endoplasmic reticulum of endothelial cells, pericytes, lymphocytes, macrophages and satellite cells. Other types of inclusions were also observed. The pathogenesis of the disease is discussed.