In PV and ET spliceosome mutations have been shown to adversely affect overall survival (SF3B1, SRSF2 in ET, and SRSF2 in PV) and myelofibrosis-free survival (U2AF1, SF3B1 in ET), while TP53 mutations predicted the risk of leukemic transformation in ET [26]. Here, SF3B1 is linked to myelofibrosis.