KMT2A and acute lymphoblastic leukemia: To the Editor: The (t;411) (q21q23) chromosomal translocation fuses lysine methyltransferase 2A (KMT2A) to ALF transcription elongation factor 1 (AFF1), the most common KMT2A fusion partner, and is prevalent in B cell precursor acute lymphoblastic leukemia (BCP-ALL) in both adults and children (1).