Patients with MDS, chronic myelomonocytoic leukemia (CMML), or chronic lymphocytic leukemia (CLL) acquire mutations in the spliceosomal components SF3B1, SF1, PRPF40B, and U2AF35 besides mutations in the splicing factor SRSF2 and ZRSR2, a component of U11/U12 di-snRNP, (Armstrong et al., 2018). Here, PRPF40B is linked to B-cell chronic lymphocytic leukemia.