RNA splicing is a crucial post-transcription process that regulates gene expression and increases genomic diversity.[1] Recently, somatic mutations involving core components of the RNA splicing machinery were detected in myelodysplastic syndrome (MDS).[2, 3] Mutations of the splicing factor (SF) genes occur most frequently in SRSF2, U2AF1, and SF3B1, but also ZRSR2, U2AF2, SF1, SF3A1, PRPF40B, PRPF8 and LUC7L2,[2] with a strong genotype and phenotype association.[4-6] Some of these mutations showed prognostic relevance in MDS, however, discrepancies exist among different studies.[7]. This evidence concerns the gene U2AF1 and myelodysplastic syndrome.