Pathological features of inflammatory myopathy as a manifestation of chronic graft-versus-host disease after allogeneic bone marrow transplantation

Chronic graft-versus-host disease (cGVHD) is the most important complication resulting in the death of bone marrow transplantation (BMT) survivors. It is also a relatively rare cause of inflammatory myopathy (IM). We report the case of a 46-year-old woman who developed severe cGVHD-related IM after BMT for myelodysplastic syndrome. She presented with severe muscle pain and weakness with cGVHD-related symptoms in other organs. Myopathological analysis showed moderate cell infiltration with remarkable necrotic and regenerative fibers. Sarcoplasm and capillaries expressed C5b9 and myxovirus resistance protein 1. Non-necrotic fibers in perifascicular regions expressed MHC-II. Steroid therapy did not sufficiently control cGVHD-related IM, and the patient was concurrently treated with an immunosuppressant. Our findings show that IM is a key manifestation of cGVHD and that the expression of interferon-inducible proteins in muscle pathology is useful for identifying cGVHD-related IM.