The chromosomal translocation of the mixed-lineage leukemia 1 gene (MLL1, also known as MLL or KMT2A) accounts for ~9% of adult, ~5% of children, and 80% of infants cases in acute lymphoblastic leukemia (ALL), together with over 10% of adult cases, ~15% of children, and above 70% of infant cases in acute myeloid leukemia (AML) [88,89]. The gene discussed is KMT2A; the disease is acute myeloid leukemia.