Persistent Antigen A after Minor ABO-Incompatible Hematopoietic Stem Cell Transplantation in Children: Two Case Reports

Introduction: ABO blood type changes after ABO-incompatible hematopoietic stem cell transplantation (HSCT). Most non-hematopoietic tissues retain the expression of the patient’s own ABO antigens, which may adsorb from the plasma onto the donor’s red blood cells (RBCs). Because of this phenomenon, a persistent patient’s A and/or B antigen could be detected in the laboratory, despite 100% white cell donor chimerism. Adsorption of the patient’s soluble ABO antigens on the newly formed RBCs complicates the interpretation of the patient’s blood type and decision of transfusion therapy. Case Presentation: The first case report is a 6-year-old girl, A, D+, with T-cell acute lymphoblastic leukemia (ALL), transplanted with HLA-matched unrelated group O, D+ bone marrow. A second case report describes an 8-year-old girl, AB, D−, with ALL transplanted with an HLA-matched related group B, D+ bone marrow. The presence of persistent antigen A was registered in both patients more than 1 year after HSCT, despite complete donor chimerism. Conclusion: The weak expression of ABO antigens on RBCs after HSCT should be examined in detail for proper planning of transfusion therapies.