Expanding the spectrum of post-HSCT hemolysis: from passenger lymphocyte syndrome to host- and graft-associated alloimmune hemolytic anemia.

Immune-mediated alloimmunization and hemolytic anemia can complicate ABO-incompatible hematopoietic stem cell transplantation (HSCT). After major ABO-incompatible HSCT, clinical manifestations may include pure red cell aplasia and delayed hemolysis. Passenger lymphocyte syndrome and delayed hemolysis are typical complications of minor ABO-incompatible HSCT. Because delayed hemolysis after major or minor ABO mismatch may be indistinguishable, the terms host-associated alloimmune hemolytic anemia and graft-associated alloimmune hemolytic anemia have been tentatively proposed to distinguish these conditions according to their host or graft origin. However, the rarity of these subgroups may limit the clinical utility of this classification. Management across the clinical spectrum includes transfusion support, plasmapheresis, and therapeutics related to immunomodulatory therapies.