Mutations in IDH1 or IDH2, present in ∼15–20% of acute myeloid leukemia (AML) cases, generate the oncometabolite (R)-2-hydroxyglutarate (2-HG), enforcing a hypermethylated, differentiation-refractory state (Pirozzi and Yan, 2021). The gene discussed is IDH2; the disease is acute myeloid leukemia.