The somatic mutation JAK2-V617F is frequently observed in BCR/ABL1-negative myeloproliferative neoplasms (MPNs): 92% in polycythemia vera (PV), 55% in essential thrombocythemia (ET), and 50% in primary myelofibrosis (PMF) [3]. Here, JAK2 is linked to essential thrombocythemia.