The prevalence of TET2 mutations gradually increased with age, from 7% in adults younger than 30 to 32% in patients aged 70 years or older (P < .001).21 Mutation of at least one copy of the TET2 gene was detected in 49/247 (19.8%) patients with secondary acute myeloid leukemia, including both AML with MRC (n=201) or therapy-related (n=46) leukemias. The gene discussed is TET2; the disease is leukemia.