De novo development of JAK2V617F-positive polycythemia vera following allogeneic hematopoietic stem cell transplantation: a report of two rare cases.

INTRODUCTION: Post-transplant erythrocytosis following allogeneic hematopoietic stem cell transplantation (allo-HSCT) is rare and has been reported mainly in patients with aplastic anemia and, less frequently, after transplantation for other hematologic conditions. Here, we present two cases of JAK2V617F-positive polycythemia vera (PV) developing after allo-HSCT performed for chronic myeloid leukemia (CML) and myelodysplastic syndrome (MDS).

CASE PRESENTATIONS: Case 1: The patient, who underwent allo-HSCT for the diagnosis of MDS. He was diagnosed with JAK2V617F-positive PV, 48 months after transplantation. Case 2: The patient with chronic-phase CML underwent allo-HSCT while in hematologic remission. Approximately 10 years later, the patient was diagnosed with JAK2V617F-positive PV.

DISCUSSION: Possible explanations for the development of a JAK2V617F mutation after allo-HSCT include the expansion of a pre-existing but clinically silent mutant clone in the donor, or the emergence of de novo mutations in donor or recipient cells as a result of proliferative stress, immunosuppression, or prior chemotherapy.