ASXL1 mutations occur frequently in MDS/MPNs, particularly chronic myelomonocytic leukemia (CMML) (~ 43–49% of patients) [38, 39] and juvenile myelomonocytic leukemia (JMML) (7–8%) [40, 41], frequently in MDS (15–21%) [42, 43], and occasionally in MPN (8–10%) [44, 45], AML (3–10%) [46, 47], and CHIP (< 4%) [37]. The gene discussed is STUB1; the disease is myelodysplastic syndrome.