According to the World Health Organization (WHO) 2016 classification, three diseases associated with the Janus kinase 2 (JAK2)/calreticulin (CALR)/myeloproliferative leukemia virus oncogene (MPL) mutation (polycythemia vera, essential thrombocythemia (ET), and primary myelofibrosis) and four clinicopathological diseases (chronic myeloid leukemia, chronic neutrophilic leukemia, chronic eosinophilic leukemia, and not otherwise specified-unclassifiable) are included in chronic myeloproliferative neoplasms [1,2]. The gene discussed is CALR; the disease is acquired polycythemia vera.