The somatic V617F gain-of- function mutation in exon 14 of JAK2 gene, and less commonly exon 12 mutation of JAK2 have found in greater than 95% of patients with polycythemia vera and about 50% of patients with essential thrombocythemia and myelofibrosis [6]‐[8]. This evidence concerns the gene JAK2 and essential thrombocythemia.