The level of DNA methyltransferase 1 (DNMT1), which is the enzyme implicated in the maintenance of DNA methylation at each cell division, declines with age in T cells, causing aberrant methylation profiles that can lead to malignant transformation or autoimmunity, such as with myelodysplastic syndromes or VEXAS, which is now the archetype of the acquired auto-inflammatory disease occurring in elderly men [32,39,40,41]. The gene discussed is DNMT1; the disease is Autoimmunity.