IDH mutations were detected at a frequency of 3-5% in MDS, 1-4% in MPN, 9% in MDS/MPN including CMML, 15% in AML transformed from MDS, 22% in AML transformed from MPN, 10% in AML transformed from MPN/MDS and 22% in high risk MDS associated with del(5q) [11-13, 20-23]. The gene discussed is IDH2; the disease is myeloproliferative disorder.