Ultrastructural changes in granulomatous myopathy

Summary Muscle biopsies from four middle-aged to elderly women with a 3–16-years' history of slowly progressive proximal muscle weakness showed noncaseating granulomas. Although two of them had clinical features suggestive of sarcoidosis, the other two had not. No distinct differences in the structural changes of these cases were noted by light or electron microscopy. The granulomas were comprised of epithelioid cells, Langhans type giant cells, lymphocytes, macrophages, and small numbers of plasma cells, monocytes, and mast cells. Some lymphocytes appeared to be transformed. The damaged muscle fibres were mostly located near the granulomas. Some of them were infiltrated by epithelioid cells, macrophages and mononuclear cells similar to lymphocytes. These cells were seen between the basement and plasma membranes of the muscle fibres. The muscle fibres showed various degenerative changes. Regeneration of muscle fibres was also observed. Filamentous intranuclear inclusions were present in two cases.