Passenger Lymphocyte Syndrome (PLS): A Single-center Retrospective Analysis of Minor ABO-incompatible Liver Transplants

Background and Aims: Due to the shortage of donor livers, minor ABO-incompatible liver transplantations are commonly performed. Together with the allograft, immunocompetent B-lymphocytes, called passenger lymphocytes, are transplanted. In case of minor ABO-incompatibility, these passenger lymphocytes produce antibodies directed towards the recipient's red blood cells, which causes immune-mediated hemolysis, also known as the passenger lymphocyte syndrome (PLS). Although this is a self-limiting disorder, serious complications can occur, including graft failure. Retrospectively, we evaluated the role of PLS in minor ABO-incompatible liver transplantations performed at our center. Methods: A retrospective analysis was conducted for all minor ABO-incompatible liver transplantations performed at the Antwerp University Hospital between 2003 and 2015. All patient files were inspected for clinical and laboratory findings. In cases of PLS diagnosis, the applied treatment was also studied. Results: In total, 10 patients underwent a minor ABO-incompatible liver transplantation and 4 showed signs of PLS. All 4 PLS patients were treated with different therapeutic strategy, corresponding to the severity of hemolysis. In all 4 cases, PLS resolved following treatment. Conclusion: When performing minor ABO-incompatible liver transplantations, knowledge of PLS is elemental. Next to a high index of clinical suspicion, we suggest routine screening for markers of hemolysis, with emphasis on haptoglobin level and direct antiglobulin test, weekly in the first 4 weeks post-transplantation as well as in case of a sudden hemoglobin drop within the first 3 months after transplantation. Peri- and postoperative transfusion support using donor-compatible blood has been suggested to prevent the occurrence or limit the extent of hemolysis.