In 2013, CALR mutations were first identified as driver mutations in myeloproliferative neoplasm (MPN) and were found in 70–80% of patients with JAK2 V617F-negative essential thrombocythemia (ET) and primary myelofibrosis (PMF), with characteristic clinical findings [2,3]. The gene discussed is CALR; the disease is myeloproliferative neoplasm.