IDH1 and chronic myelomonocytic leukemia: Mutations involving IDH1 (isocitrate dehydrogenase—chromosome 2q34) and IDH2 (chromosome 15q26.1) are uncommon in CMML (<5%) and are mutually exclusive with TET2 mutations.7, 40 IDH1/2 normally participates in the citric acid cycle and converts isocitrate to 5-alpha-ketoglutarate (Figure 4).