ASXL1 and myelodysplastic syndrome: In addition, the mutational landscape of MDS in children differs from that in adults; mutations in genes for epigenetic regulation (e.g., TET2, ASXL1, and DNMT3A) and RNA splicing (e.g., SF3B1 and U2AF1) are rare in pediatric primary MDS (2%), whereas mutations in genes from the RAS/MAPK pathway are common (45%) [64].