Activation of complement and coagulation in juvenile dermatomyositis.

In patients with juvenile dermatomyositis (JDM), small vessel occlusion and thrombosis result in a decrease in the capillary: muscle fiber ratio. We studied 15 patients with JDM. Six of 7 patients with clinically active JDM had elevated levels of C3d. Moreover, concentrations of fibrinopeptide A and factor VIII-related antigen were significantly increased in patients with clinically active JDM.