JAK2 and myeloproliferative neoplasm: Myeloproliferative neoplasms (MPNs) occur as a result of clonal outgrowth of hematopoietic stem cells (HSCs) carrying a somatic mutation, most commonly in JAK2 (JAK2V617F), endowing them with cytokine independent growth and ensuing in the overproduction of mature and differentiated cells of cells of the myeloid lineage [1,2,3,4,5].