Myositis associated with graft-versus-host disease.

A polymyositis syndrome has been described as a rare complication in patients who develop chronic graft-versus-host disease after allogeneic bone marrow transplantation. Chronic graft-versus-host disease is a cellular immune-mediated donor bone marrow versus patient rejection reaction, which may also lead to an autoimmune pathologic process. Chronic graft-versus-host disease-related polymyositis appears to be very similar to idiopathic myositis in its clinicopathologic presentation; chronic graft-versus-host disease-related myositis responds well to prednisone but cyclosporine may be an important component of second-line therapy due to its efficacy in controlling underlying chronic graft-versus-host disease.