Chromosomal rearrangements involving the lysine (K)-specific methyltransferase 2 A (KMT2A, located on chromosome 11q.23.3, and previously known as mixed lineage leukemias or MLL) are associated with both de novo and therapy-induced infant and pediatric acute leukemias (Fig. 1A) [3]. Here, KMT2A is linked to acute leukemia.