In 2013, two groups reported the discovery of mutations in the CALR gene in Myeloproliferative Neoplasms (MPNs), particularly in 60–80% of JAK2 and MPL unmutated Essential Thrombocythemia (ET) and Primary Myelofibrosis (PMF) patients4,5. Here, JAK2 is linked to myeloproliferative disorder.