KMT2A and acute myeloid leukemia: MLL (mixed-lineage leukemia, now renamed Lysine [K]-specific MethylTransferase 2A, KMT2A) on chromosome 11q23 is mutated in up to 10% of adult AML cases and represents another peculiar example of gene defining an AML subtype with an exquisite chemorefractoriness [24].