Clinical Outcomes of Rh(D)-Incompatible Allogeneic Haematopoietic Stem Cell Transplantation: A Single-Centre Retrospective Case Series with a Narrative Literature Review.

Rh(D)-negative individuals are relatively rare in the Chinese population, and clinical experience with Rh(D)-incompatible allogeneic haematopoietic stem cell transplantation (allo-HSCT) remains limited. Compared with ABO incompatibility, the immunohaematological consequences of Rh(D) mismatch in allo-HSCT are less well defined. Herein, we report a single-centre retrospective case series of four patients receiving Rh(D)-incompatible allo-HSCT at our institution, including two Rh(D)-negative recipients with Rh(D)-positive donors and two Rh(D)-positive recipients with Rh(D)-negative donors. We systematically evaluated post-transplant transfusion strategies, haematological recovery, anti-D alloantibody seroconversion, haemolysis or graft-versus-host disease (GVHD), and long-term survival outcomes. During a median follow-up of 36 months (range, 24-48 months), none of the patients developed detectable anti-D alloantibodies. Only one patient exhibited laboratory evidence of subclinical haemolysis responsive to low-dose prednisone, and another patient developed grade II acute gastrointestinal GVHD controlled by immunosuppressive agents. Nevertheless, all patients achieved sustained haematological engraftment without transplant-related mortalities. Combined with data from a narrative literature review, our single-centre observations are consistent with prior studies showing low risks of clinically significant haemolysis and anti-D alloimmunisation after Rh(D)-incompatible allo-HSCT. Rh(D) mismatch does not appear to be associated with severe transplant complications in our limited cohort, but these findings cannot be generalised broadly given the extremely small sample size. Rigorous peri-transplant transfusion management and regular post-transplant serological monitoring are still mandatory for Rh(D)-mismatched recipients.