Researchers have reported DNA hypermethylation and hypomethylation in a variety of genes in individuals with periodontitis and SLE.15 , 16 These epigenetic changes, in turn, can be caused by an increase or decrease of enzymes involved in epigenetic mechanisms such as methylenetetrahydrofolate (MTHFR) and DNA methyltransferase (DNMT), for example. The gene discussed is MTHFR; the disease is systemic lupus erythematosus.