Based on the paradigm that areas of somatic UPD contain homozygous mutations, we sequenced TET2 and DNMT3A. We also searched for mutations in other genes known to be involved in myeloid diseases that share pathophysiologic, morphologic, and clinical similarities with mastocytosis, such as CMML and myelofibrosis [15], [22]. The gene discussed is DNMT3A; the disease is chronic myelomonocytic leukemia.