Recurrent mutations have been reported in MDS/MPN in the spliceosome components SF3B1, SRSF2, U2AF1 and ZRSR2, affecting overall up to 65% of cases, while mutations in PRPF40B, SF3A1, SF1 and U2AF2 are rare (<3%). The gene discussed is U2AF1; the disease is myeloproliferative disorder.