JAK2 V617F activating mutation in chronic myelomonocytic leukemia

JAK2V617F mutation was identified in 5 of 65 consecutive patients with newly diagnosed chronic myelomonocytic leukemia (CMML). Patients with JAK2V617F mutation presented all with a marked splenomegaly and had a significantly higher RBC count, haemoglobin level and neutrophil count than patients without the mutation. Bone marrow biopsies of mutated CMML showed in all cases marked myeloid hyperplasia, moderate to marked megakaryocytic hyperplasia, occasionally clustered megakaryocytes, and mild to moderate reticulin fibrosis; three showed an increased number of dilated sinusoids. Our results indicate that JAK2V617F mutation is associated with clinical and morphologic features of the myeloproliferative type of CMML.