Specifically recurrent mutations affecting the highly conserved arginine (R) residue at codon 132 (R132) of IDH1 and at codons R140 and R172 of IDH2 have been identified in 15%–20% of all AML and 25% to 30% of patients with CN-AML [11,22,31]. The gene discussed is IDH2; the disease is acute myeloid leukemia.