Coexistence of chronic lymphocytic leukaemia and polycythemia vera

We report a rare case of coexistence of chronic lymphocytic leukaemia (CLL) and polycythemia vera (PV) in a patient initially diagnosed and treated for CLL. A 61-year-old man presented with fatigue and night sweats, with laboratory tests showing elevated haemoglobin, hematocrit (HCT), leukocyte count and splenomegaly. Peripheral blood smear revealed lymphocytosis with basket cells, and flow cytometry confirmed CLL (RAI stage II). FISH analysis was negative for del13q, del11q, trisomy 12, del 17p and del6q. Chemotherapy was started because of B symptoms. Persistent splenomegaly and elevated HCT at follow-up prompted further evaluation, which revealed a JAK2 V617F mutation and an erythropoietin (EPO) level <1 mIU/mL, confirming PV. The patient achieved remission for CLL, but required hydroxyurea and acetylsalicylic acid for PV. The coexistence of CLL and PV is rare and the underlying mechanisms are not well understood, although a common clonal haematopoietic stem cell origin or germline mutations are possible explanations. Although chemotherapeutic agents are known to induce PV, the elevated HCT at the time of CLL diagnosis suggests a pre-existing relationship between the two diseases. Therefore, elevated HCT in CLL patients should prompt consideration of PV.