JAK2 and primary myelofibrosis: A single nucleotide mutation of the janus kinase 2 gene (JAK2 V416F) is the most frequent among MPN driver mutations, occurring in more than 90% of patients with Polycythemia vera (PV) and about 50% of patients with Essential thrombocytosis (ET) and Primary myelofibrosis (PMF), respectively (74).