Chromosomal translocations, inversions, amplifications and complex rearrangements at the 11q human genomic locus encoding the lysine methyl transferase 2 A gene (KMT2A), also known as mixed lineage leukemia gene (MLL), are a hallmark of acute lymphoblastic leukemia (ALL) in infants and of therapy-induced acute myeloid leukemia/myelodysplastic syndrome (AML/MDS) in adults (1–3). Here, KMT2A is linked to acute lymphoblastic leukemia.