[Muscle granuloma: anatomoclinical correlation and immunohistochemistry in seven cases]

Granulomatous inflammation is infrequently observed in muscle biopsy. We report a series of 7 patents presenting with granulomas in muscle. Two of them had a history of sarcoidosis In 4 other cases, muscle Involvement revealed systemic sarcoidosis. Among the 6 cases of sarcoidosis, we observed 2 with acute myositis and 4 chronic forms. The last patient presented with polymyositis in association with melanoma. In sarcoidosis, muscle biopsy showed a granulomatous inflammation of varying intensity, which was generally associated with mononuclear inflammatory cells. Most of granulomas were located in the perimysium and the endomysium and necrosis was absent. Inflammatory cells were predominantly macrophages and CD4 positive lymphocytes. On the contrary, in the case of paraneoplastic polymyositis,granulomas were rare, most of inflammatory cells were CD8 positive lymphocytes and numerous areas of necrosis were observed. Class I MHC molecules were expressed on the membrane of muscle fibers. As a general rule, requisite examinations must be performed to search for sarcoidosis in patients exhibiting granulomas on muscle biopsy.