Most of leukemia-associated IDH1 and IDH2 mutations occur at the level of arginine residues present in the catalytic pocket of the enzyme, with the IDH1 mutations occurring mostly at arginine 132 (R132H or R132C or R132L or R132S or R132G) and those of IDH2 occurring mostly at arginine 172 or 140. The gene discussed is IDH1; the disease is leukemia.