Additional sex combs-like 1 (ASXL1) gene is highly mutated in a spectrum of myeloid malignancies, including ~49% of chronic myelomonocytic leukemia (CMML) [1], ~10% of acute myeloid leukemia (AML) [2], ~21% of myelodysplastic syndromes (MDS) [3], ~10% of myeloproliferative neoplasms (MPN) [4], and ~8% of juvenile myelomonocytic leukemia (JMML) [5]. The gene discussed is ASXL1; the disease is juvenile myelomonocytic leukemia.