MTHFR and periodontitis: 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.