PTPN21 and leukemia: Our results revealed a significant enrichment of mutations in epigenetic regulators from relapsed samples, with recurrent somatic mutations in SETD2, CREBBP, KDM6A and NR3C1. The relapsed samples were also enriched in signaling factor mutations, including KRAS, PTPN21, MYC and USP54. Furthermore, we are the first to reveal the clonal evolution patterns during leukemia relapse after allo-HSCT.