It is now recognized that approximately 8% and 12% of acute myeloid leukemias harbor an IDH1 or IDH2 mutation, respectively, with IDH mutations also present in a minority of other myeloid malignancies such as myelodysplastic syndrome (MDS) and accelerated myeloproliferative neoplasms (MPNs)2,3. The gene discussed is IDH1; the disease is myelodysplastic syndrome.