In the vast majority of IDH mutated gliomas (>90%), these mutations are located at codon 132 of IDH1 and result in an arginine-to-histidine (R132H) substitution at the active site, although other mutations affecting the corresponding arginine residue in IDH1 or IDH2 have been described as well [1,2,3]. The gene discussed is IDH1; the disease is central nervous system cancer.