The phenotype ofIDH1 orIDH2 mutant AML is similar, characterized by the gain-of-function, neomorphic mutant IDH activity producing 2-HG, which in turn impairs cellular differentiation.IDH1 mutations (IDH1m) are slightly less common than IDH2 mutations in AML; the former are seen in about 8 to 10% of patients, mostly those with normal karyotype AML, and the most commonly co-occurring mutations are in theNPM1,DNMT3A, andFLT3 genes86. The gene discussed is DNMT3A; the disease is acute myeloid leukemia.