Clinically significant anti-A(1) in a presumed ABO-identical hematopoietic stem cell transplant recipient: a case report.

Background: Subgroups of the blood group A (ABO) are generally not considered ABO incompatible for hematopoietic progenitor cell (HPC) transplant.

Case Report: A 54-year-old female presented for HPC transplantation for acute leukemia. No HLA-matched donor was identified, so she received a peripheral blood stem cell graft from an HLA-mismatched unrelated donor. On pretransplant testing, both the donor and the recipient typed as blood group A. On Day +67 after transplant, the recipient had a transfusion reaction consisting of an increase in temperature, rigors, and shaking chills during infusion of a unit of group A red blood cells (RBCs). A transfusion reaction workup revealed an ABO discrepancy with both anti-A (1+) and anti-B (3+) identified in the patient's serum as well as a positive direct antiglobulin test with monoclonal anti-IgG antisera. Anti-A(1) were identified serologically and in an eluate. Hemolysis was clinically significant, requiring blood transfusion. No ABO typing discrepancies were found on pretransplant testing in either the recipient or the donor. DNA sequencing for blood group A subgroups performed after the transfusion reaction on blood collected before the transplant showed the donor to be type A(1) and the recipient as A(2) . Unfortunately, the patient experienced graft failure requiring reconditioning and reinfusion of additional cells from the original HPC donor. On Day +94 after the second transplant, the patient died with severe acute gastrointestinal graft-versus-host disease.

Conclusion: This report describes a blood group A(2) patient who developed an anti-A(1) causing clinically significant hemolysis after HPC transplant from an A(1) donor.