This study found that TET2 mRNA and TET2 protein expression was lower in the BMMNC of MDS patients than in normal controls, and TET2 mRNA relative expression was inversely correlated with IPSS and the burden of malignant clone, suggesting that TET2 was a protective gene for MDS patients and an indicator for evaluating the state of illness. The gene discussed is TET2; the disease is myelodysplastic syndrome.