Delayed massive immune hemolysis mediated by minor ABO incompatibility after allogeneic peripheral blood progenitor cell transplantation

BACKGROUND: Bone marrow transplantation with minor ABO incompatibility may be followed by moderate delayed hemolysis of the recipient's red cells by d onor-derived ABO antibodies. This reaction may be more severe after transpl antation of peripheral blood progenitor cells (PBPCs). CASE REPORT: A 16-year-old boy underwent an allogeneic PBPC transplant from his HLA-mismatched mother as treatment for acute myeloblastic leukemia tha t had proved resistant to induction chemotherapy. Transfusion of the unmani pulated PBPCs proceeded without any complication, despite the difference in ABO blood group (donor, O Rh-positive; recipient, A Rh-positive). On Day 7 , a rapid drop in hemoglobin to 4 g per dL was observed, which was attribut ed to a massive hemolysis. All the recipient's group A red cells were destr oyed within 36 hours. This delayed and rapidly progressive hemolytic anemia was not associated with the transfusion of the donor's plasma. Rather, the anti-A titer increased in parallel with marrow recovery, which suggested a n active synthesis of these antibodies by immunocompetent cells from the do nor against the recipient's red cells. The mother's anti-A titer was retros pectively found to be 2048. Her unusually high titer is probably due to pri or sensitization during pregnancies. On Day 12, the patient developed grade IV graft-versus-host disease, which proved resistant to all treatments ins tituted and led to his death on Day 35. CONCLUSION: PBPC transplantation with minor ABO incompatibility may be asso ciated with significant risk of massive delayed hemolysis.