TNF-α is one of the most important mediators of joint and periodontal inflammation.32,66 It induces the differentiation of MN/MP lineage cells into OCs,67 increases RANKL expression by osteoblasts, and causes bone resorption.68 Another important role of TNF-α is to induce the production of other inflammatory cytokines, such as IL-1β and IL-6, which attract leukocytes and promote an inflammatory environment in the synovium.69 In RA patients with periodontitis, the level of TNF-α is correlated with the severity of periodontal disease,3 and anti-TNF-α treatment improved both diseases.70 The gene discussed is TNFSF11; the disease is periodontitis.