While the pathogenesis is not yet completely elucidated, the biological hallmark of PMF consists of an aberrant activation of JAK-STAT pathway derived from the mutation in the MPN driver genes, JAK2 V617F (50–60%) [3,4], Calreticulin (CALR) (20–25%) [4,5] and MPL (5%) [4,6]. The gene discussed is JAK2; the disease is myeloproliferative disorder.