Passenger Lymphocyte Syndrome Following Minor ABO-incompatible Liver Transplantation: A Case Report

Passenger lymphocyte syndrome (PLS) is a graft-versus-host immune complication after solid organ or hematopoietic stem cell transplantation, typically arising from minor ABO or Rh incompatibility. It is caused by the transfer of viable donor B lymphocytes that produce alloantibodies against recipient red blood cell (RBC) antigens. The syndrome presents as delayed, immune-mediated hemolysis and can be clinically significant.

We report a 51-year-old woman (blood group B/Rh-positive) who underwent liver transplantation from a blood group O/Rh-positive donor. On postoperative day 9, she developed jaundice and a significant drop in hemoglobin, with no overt clinical signs of hemorrhage. Liver biopsy revealed moderate T-cell mediated rejection and laboratory workup confirmed immune-mediated hemolysis, consistent with PLS. Management included donor compatible red blood cell transfusion, corticosteroids, intensified immunosuppression, and monoclonal antibodies (rituximab), which resulted in stabilization and subsequent resolution of hemolysis.

Although rare, PLS should be considered in the differential diagnosis of early post-transplant anemia. Prompt recognition and appropriate transfusion strategy, with immunomodulatory therapy in severe cases, are crucial for favorable outcomes.