Mutations of the TET2 gene, which encodes a 2-oxoglutarate/Fe2+ oxygenase which catalyzes the conversion of methylcytosine to hydroxymethylcytosine, are frequently mutated in myeloid malignancies including 20–25% of MDS and 12–15% of MPN [27]. The gene discussed is TET2; the disease is myeloproliferative disorder.