[Pure red cell aplasia following the rapid reduction and discontinuation of cyclosporine for mixed chimerism after allogeneic bone marrow transplantation].

A 19-year-old male with therapy-related myelodysplastic syndrome underwent allogeneic bone marrow transplantation with reduced-intensity conditioning from his HLA-identical sibling whose ABO blood type exhibited major incompatibility with the patient. After post-transplantation 1 month, chimerism analysis of the bone marrow revealed mixed chimerism with 30% of recipient cells, and after post-transplantation 3 months, complete remission was maintained; however, recipient granulocytes were elevated up to 50% per the chimerism analysis. Next, pancytopenia developed following the rapid discontinuation of the immunosuppressive agent. Although neutrophils and platelets spontaneously recovered, anemia progressed. Based on severe erythroid hypoplasia in the bone marrow and the elevation of anti-ABO isohemagglutinin against donor-derived red blood cells, the patient was diagnosed with pure red cell aplasia (PRCA) following hematopoietic cell transplantation. Because complete chimerism was attained at the PRCA onset even for B cells, we decided to conservatively manage PRCA with only red blood cell transfusion. Notably, after 2 months of the PRCA onset, anemia improved. This case suggests that the therapeutic strategy for PRCA following hematopoietic cell transplantation should be determined by considering the status of each patient, including chimerism.