Concomitant JAK2 V617F-positive polycythemia vera and B-cell chronic lymphocytic leukemia in three patients originating from two separate hematopoietic stem cells.

The simultaneous occurrence of polycythemia vera (PV) and chronic lymphocytic leukemia (CLL) is a rare event that offers a possibility to study their common origin. PV originates from self-renewing hematopoietic stem cells (HSC) with both lymphoid and myeloid potential(–3). It has been reported that CLL also originates from self-renewing HSC with a potential for both lymphoid and myeloid differentiation(4, 5). We report 3 females with concomitant CLL and PV whose X-chromosome inactivation patterns of the neoplastic cells revealed that granulocytes/platelets and B-lymphocytes used different X-chromosome alleles. These data indicate that both PV and CLL have arisen independently and from different HSC.