ABL1 and primary myelofibrosis: Polycythemia vera (PV) with a prevalence of 44 to 57 per 100 000 and essential thrombocytosis (ET) with a prevalence of 38 to 57 per 100 000 are much more common than primary myelofibrosis (PMF), which has a prevalence of 4 to 6 per 100 000.1 In CML, hybrid BCR-ABL gene as a result of translocation (9,22) encodes a fusion protein that leads to activation of ABL tyrosine kinase and subsequent uncontrolled production of mature and maturing granulocytes.