OBJECTIVETo study the role of flow cytometry (FCM) in detection of polymorphic post-transplant lymphoproliferative disorders (PTLD).

METHODS AND RESULTSTwo patients presented with fever and multiple lymphadenopathy on day 46 and day 50 respectively after successful allogeneic hematopoietic stem cell transplantation (allo-HSCT). The symptoms couldn't be controlled by antibiotics. The polymorphic PTLD was diagnosed based on the elevation of bone marrow EB virus DNA and detection of subsets of light chain restricted B cells and/or plasma cells in peripheral blood (PB) samples. The lymphocyte immunophenotypes from PB and/or bone marrow (BM) samples were serially tested by FCM after lowering the dose of immunosupressive agents and treating with antivirus drugs, anti-CD20 antibodies, and cytotoxic T cell infusion. B cells were undetable in two patient, but monoclonal plasma cells appeared or maintained. One patient died after two weeks. Another patient was still on treatment. B cells and plasms cells couldn't be detected in her PB, but there were monoclonal plasma cells in her BM. FCM have a prominent advantage in detect polymorphic PTLD, since it can effectively recognize different cell groups in blood and identify monoclonal subsets. Besides, the immunophenotype of plasma cells in polymorphic PTLD might be different from that in typical plasma cell myeloma.

CONCLUSIONPolymorphic PTLD can be detected and followed up by FCM. BM is more suitable than PB for monitoing the disease. Besides lymph node biopsy, B cell abnormaliity could be detected in PB in allo-HSCT patients.