Their abnormal expression is frequently observed in lymphoid, myeloid and mixed-lineage leukaemias (MLL), and is characteristic of translocations involving the MLL gene.12 High-level expression of HOXA genes can also be seen in leukaemia patients without MLL translocations13, 14 and confers poor prognosis in both T-ALL and acute myeloid leukaemia (AML)12, 15 thus emphasizing the need for further research to identify key downstream mediators of the leukaemic phenotype. The gene discussed is KMT2A; the disease is acute myeloid leukemia.