Acquired somatic mutations affecting the R132 residue of isocitrate dehydrogenase 1 (IDH1) and the R172 residue of IDH2 have been initially described in gliomas, mainly in oligoastrocytic tumors. 1 More recently, mutation of the IDH1 gene has been reported in de novo acute myeloid leukemia (AML). 2 The prevalence of IDH1 mutations in de novo AML ranges between 5–9% of cases. They are strongly associated with the normal karyotype and are more frequent in patients with NPM1 mutation. IDH1 mutations have no impact on event-free survival in AML patients, except that they have an unfavorable effect on event-free survival in those with intermediate-risk karyotype. 3, 4 The fourth exon of both IDH1 and IDH2 genes encodes three arginine residues (R100, R109 and R132 in IDH1 and R140, R149 and R172 in IDH2) that are important for the activity of the proteins. 5

Here we have analyzed the sequence of the fourth exon of IDH1 and IDH2 genes established from the bone marrow DNA of 100 cases of myelodysplastic syndrome (MDS) including all subtypes of the WHO 2008 classification, 90 cases of MDS/myeloproliferative neoplasm (MPN), including 88 cases of chronic myelomonocytic leukemia and 2 cases of refractory anemia with ringed sideroblast and thrombocytosis, and 41 cases of AML post-MDS and AML post-MDS/MPN, referred to as secondary AML (sAML). To identify associations between molecular events, we also established the TET2 and JAK2 status of the samples.