Acute Lymphoblastic Leukemia Transformation in Polycythemia Vera: A Rare Phenomenon.

Leukemic transformation in patients diagnosed with polycythemia vera (PV) is associated with poor prognosis and median survival not exceeding 3 months. To date only a few cases of post-PV acute lymphoblastic leukemia (ALL) have been reported. A 64-year-old female patient developed ALL 4 years after she had met PV criteria. At PV diagnosis a molecular study was positive for the JAK2V617F mutation. Due to high risk features (history of deep vein thrombosis) she was treated with hydroxyurea (HU) with moderate efficacy. She became anemic and thrombocytopenic with mild leukocytosis while still on HU. Blood and bone marrow smears revealed 40 and 100 % of blast cells, respectively. The immunophenotyping of blasts was consistent with a diagnosis of early precursor B cell ALL. She was found to be positive for the JAK2V617F mutation. Patient received an ALL induction regimen and achieved complete remission with negative minimal residual disease by flow cytometry. The post-chemotherapy study for the JAK2V617F mutation was positive. Patient has remained in remission for 4 months. A suitable donor searching was initiated. Post-PV ALL is an extremely rare phenomenon. Due to poor prognosis, an allogeneic stem cell transplantation should be considered in fit patients who achieved remission.