The discovery of a novel JAK2V617F mutation, which is found in 50–90% of all classical MPNs and results in a substitution of valine to phenylalanine in the JAK2 gene, significantly contributed to the discovery of the molecular pathogenesis of myeloproliferative neoplasms [5,7,8,9,10]. The gene discussed is JAK2; the disease is myeloproliferative disorder.