NRAS and juvenile myelomonocytic leukemia: NRAS/KRAS mutations have been found in 20–25% of patients with acute myeloid leukemia (AML) [5], 25–30% of patients with juvenile myelomonocytic leukemia (JMML) [7], and 15% of pediatric patients with B- or T-lineage acute lymphoblastic leukemia (ALL) [8, 9].