Alexis R. Peedin

Hematopoietic stem cell transplants (HSCTs) are widely used in the treatment of hematologic malignancies and bone marrow failure syndromes. ABO compatibility is typically of secondary importance, and up to 50% of HSCT are performed in ABO‐incompatible pairings. In the literature, pure red cell aplasia (PRCA) occurs in 1% to 50% of all major/bidirectional ABO‐incompatible stem cell transplants, but treatment of PRCA remains heterogeneous. Here, we report two cases in which patients with transfusion‐dependent PRCA following HSCT were successfully treated with therapeutic plasma exchange (TPE). Case 1: A 52‐year‐old type O‐positive male with acute myeloid leukemia underwent HSCT using apheresis‐derived HSCs from a fully human leukocyte antigen (HLA)‐matched, related type A‐positive male donor. He developed PRCA that was refractory to multiple therapies, so a series of 10 TPE was performed over 3 weeks. Case 2: A 21‐year‐old type A‐positive male with aplastic anemia underwent HSCT using bone marrow‐derived HSCs from a fully HLA‐matched related type B‐positive female donor. He developed PRCA that was refractory to multiple therapies, so a series of 5 TPE was performed over 2 weeks. Case 1: The patient has been transfusion independent since TPE #7, and type A red blood cells (RBCs) were seen on the ABO type after TPE #9. Case 2: The patient has been transfusion independent since after TPE #1, and type B RBCs were seen on the ABO type after TPE #5. TPE was successful in treating two patients with PRCA after ABO‐incompatible HSCT transplants. Isoagglutinin titers decreased below the level of detection for both our patients. Ultimately both patients became transfusion independent and showed evidence of erythroid cell recovery.