Relationship Between Capillary and Muscle Damage in Dermatomyositis

To assess the pathogenetic importance of capillary damage and its relationship with degenerating muscle fibers in dermatomyositis (DM), an electron microscope study of eight muscle biopsy specimens (adult and juvenile forms) and seven muscle specimens from patients with other neuro-muscular diseases was conducted. There was a 49% reduction of capillaries in the muscle specimens of DM patients. Capillary damage also was more frequent in the DM group than in control group (p<0.001). We found a striking relation between capillary and muscle damage in the DM group (p<0.002) but not in the control group. The diagnostic value of undulating tubules within endothelial cells is also discussed.