Red cell aplasia due to host type isohemagglutinins with exuberant red cell progenitor production of donor type in an ABO-mismatched allogeneic bone marrow transplant recipient.

ABO-mismatched bone marrow transplants have resulted in delayed red cell production in patients who have persistently elevated anti-ABO isohemagglutinin titers. We present a patient with chronic myelogenous leukemia who received an HLA-matched, ABO-incompatible bone marrow transplant from his sister. Post-transplant, he developed pure red cell aplasia with exuberant production of donor red cell precursors by in vitro BFU-E assay. Restriction fragment length polymorphism (RFLP) analysis of bone marrow, peripheral blood and BFU-E colonies demonstrated only donor type DNA post-transplant. However, the patient had persistently elevated isohemagglutinin titer and Ph1 chromosome-positive metaphases on chromosome analysis, indicating the presence of persistent host lymphocytes. With onset of acute graft vs. host disease (GVHD), the isohemagglutinin titer dropped, Ph1 chromosome-positive metaphases disappeared, and full hematopoietic recovery ensued. Longitudinal analysis of RFLP's, isohemagglutinin titers and chromosomes may be helpful in understanding the immunological interplay following allogeneic bone marrow transplantation.