Comprehensive genomic studies have revealed that nearly half of AML cases harbor mutations in genes regulating DNA methylation (eg DNMT3A, TET2, IDH1, IDH2) and about one-third have mutations in genes that directly or indirectly modify chromatin (eg KMT2A/MLL, ASXL1, EZH2) [2]. The gene discussed is IDH2; the disease is acute myeloid leukemia.