Abstract
We examined the role of the complement system in the pathogenesis of dermatomyositis. Using an antibody against the neoantigens of the terminal C5b–9 membrane attack complex, we performed immunocytochemical studies that localized this complex to the intramuscular microvasculature (arterioles and capillaries) of muscle biopsy specimens from 10 of 12 patients (83 percent) with childhood dermatomyositis and 5 of 19 patients (26 percent) with adult dermatomyositis. Fifty-two control specimens, including 14 from patients with polymyositis and 12 from patients with denervation atrophy (a condition known to be associated with necrotic capillaries), showed no deposition of membrane attack complex in the microvasculature. These findings indicate that the complement system is deposited, bound, and activated to completion within the intramuscular microvasculature of patients with dermatomyositis. In addition to providing further evidence for the presence of vasculopathy in dermatomyositis, these findings suggest a primary role for complement in mediating vessel injury in the disease, particularly in its childhood form. (N Engl J Med 1986; 314: 329–34.)
ALTHOUGH little is known about the pathogenesis of the idiopathic inflammatory myopathies, a considerable body of evidence suggests that the intra-muscular microvasculature may be the site of primary involvement in childhood dermatomyositis and possibly in adult dermatomyositis.
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However, the precise mechanism of vessel injury in these diseases is unknown. In 1972, Whitaker and Engel reported the presence of IgG, IgM, and complement (C3) deposits in the venules and, to a lesser extent, in the arterioles of muscle biopsy specimens from patients with childhood and adult dermatomyositis.
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On the basis of these findings, they postulated that immune-complex deposition might play a . . .
