Mutations in the epigenetic regulator genes DNMT3A, TET2 and ASXL1 are responsible for ~70% of CH cases, with most of the remaining cases driven by mutations in genes involved in RNA splicing (SF3B1, SRSF2 and U2AF1), DNA damage response (DDR) (TP53 and PPM1D), cytokine signaling (JAK2) and G-protein signaling (GNB1 and GNAS)2,3,5. The gene discussed is PPM1D; the disease is cyclic hematopoiesis.