Activating mutations of NRAS and KRAS genes were reported to occur in 18–32% of acute myeloid leukemia (AML)1,2, in 11–38% of chronic myelomonocytic leukemia (CMML)3,4 and in 25–35% of juvenile myelomonocytic leukemia (JMML) patients5,6. This evidence concerns the gene KRAS and juvenile myelomonocytic leukemia.