In 2005, it was discovered that the activating mutation in Janus kinase 2 (JAK2), mostly at codon 617 (JAK2 V617F), is involved in the development of Ph-negative MPNs, including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF) (Cazzola and Kralovics, 2014; WHO, 2017; Arber et al., 2022; Khoury et al., 2022). The gene discussed is JAK2; the disease is essential thrombocythemia.