More recent studies in PV have confirmed the adverse and age-independent impact on survival of karyotype, leukocytosis, and certain non-JAK2 mutations including SRSF2 and IDH2 [66, 67]; of note, NGS studies have revealed that over 50% of patients with PV harbor DNA sequence variants/mutations other than JAK2, with the most frequent being TET2 (18%), ASXL1 (15%), and LNK (3%) [67, 68]; combined prevalence of adverse mutations (SRSF2, IDH2, RUNX1, U2AF1) for overall, leukemia-free or myelofibrosis-free survival in PV was estimated at 5–10% [67]. The gene discussed is IDH2; the disease is myelofibrosis.