Pathologic features of muscle in systemic lupus erythematosus: a biopsy series with comparative clinical and immunopathologic observations.

Clinical evidence of skeletal muscle involvement is frequent in systemic lupus erythematosus (SLE). In order to characterize the manifestations of SLE in skeletal muscle, a biopsy series on 19 patients with SLE was studied in terms of the histologic, histochemical, and direct immunofluorescent features of skeletal muscle. The results were correlated with clinical and laboratory data. The histologic spectrum included inflammatory myopathy, vasculitis, perifascicular atrophy, and neurogenic atrophy. Histochemical examination revealed type I fiber predominance in 44 per cent of patients and selective type II fiber atrophy in 33 per cent. Direct immunofluorescent examination of skeletal muscle biopsy specimens revealed immunoglobulin and complement deposition in vessel walls, in sarcolemmal basement-membrane areas, and within non-necrotic muscle fibers. The histologic, histochemical, and immunochemical findings are correlated with the findings in other organ systems.