Regarding mutations of other RNA splicing factors, as reported in MDS, SF3B1 mutations were associated with the presence of ring sideroblasts [56,62], even leading to the proposition of a specific MDS entity [69], but in contrast to MDS, there was no positive impact of SF3B1 mutation on overall or leukemia-free survival in PMF [48,62] or in PV [53] patients. The gene discussed is SF3B1; the disease is acquired polycythemia vera.