KMT2A and acute lymphoblastic leukemia: ALL in infants is a rare subset often associated with KMT2A (also known as MLL) rearrangements (KMT2A‐r), a high leucocyte count at diagnosis, an immature or pro‐B‐cell lineage immunophenotype (CD10−) and a prenatal origin in utero (Ford et al, 1993; Biondi et al, 2000).