Polymyositis associated with thymoma and the subsequent development of pure red cell aplasia

A 53-year-old woman with polymyositis associated with thymoma subsequently developed pure red cell aplasia (PRCA). She was hospitalized because of fever and muscle weakness, and diagnosed as having polymyositis by muscle biopsy. Remarkable clinical improvement followed administration of prednisolone. Progressive anemia became evident, however, while prednisolone was being tapered. Erythroid aplasia and the presence of thymoma confirmed the diagnosis of PRCA. Further examinations revealed that cytotoxic T cells may play an important role in the pathogenesis of this case.