The childhood type of dermatomyositis

TLDR

Childhood dermatomyositis is a muscle disease in children and young adults characterized by capillary necrosis, progressive ischemia‑related muscle fiber damage, and an unknown etiology. Electron microscopy reveals endothelial undulating tubules, lymphocytes, pericytes, and pseudosatellite cells, while affected muscle fibers display mitochondrial elongation, Z‑disk streaming, focal myofibrillary loss, and occasional thick‑filament loss, with rare infarct‑like necrosis and septal inflammatory infiltrates.

Abstract

The childhood type of dermatomyositis, which occurs in children and young adults, shows a specific constellation of pathologic changes in muscle. Capillary necrosis leads to capillary loss, generally starting on the periphery of muscle fascicles. Electron microscopy discloses undulating tubules in endothelial cells, lymphocytes, pericytes, and pseudosatellite cells. The muscle fiber damage is coextensive with capillary damage and probably results from progressive ischemia. The muscle cells, before atrophying, show mitochondrial elongation, Z disk streaming, focal myofibrillary loss, and occasionally selective thick filament loss. Muscle cell necrosis is rare and limited to infarctlike lesions. Inflammatory infiltrates, if present, occur only in connective tissue septa. The cause of the capillary damage has not been determined.