Abstract:

Objective To assess pathological features of muscles as well as microvascular changes between muscle fibers in patients with dermatomyositis （DM）, and to analyze pathological differences in muscles between DM and polymyositis （PM）. Methods Specimens were obtained from involved muscles of 16 patients with DM, 5 patients with PM, and from normal muscles of 9 patients with bone trauma （controls）. Routine histopathological examination and immunohistochemical staining for CD34 and CD61 were conducted. Results Of the 16 patients with DM, 6 （37.5%） had perifascicular atrophy, 3 （18.8 %） had an obvious inflammatory cell infiltration around microvessels between muscle fibers. Perifascicular atrophy was absent in muscle specimens from patients with PM or bone trauma. The number of CD34-positive microvessels between muscle fibers was reduced in patients with DM, but normal in those with PM. CD61 was positive in perifascicular area of 10 patients （5 moderately positive and 5 weakly positive） with DM, with an expression rate of 62.5%, however, only 1 case of PM was weakly positive for CD61, and all the controls were negative. Conclusions There is a decrease in the number of microvessels but an enhancement of neovascularization between muscle fibers in involved muscles of patients with DM, which may serve as a pathological marker to distinguish DM from PM.

Key words: CD61