HLA-DRB1 and periodontitis: Periodontitis and RA exhibit several common features, including shared pathogenetic processes, cytokine profiles, inflammatory markers and genetic associations, such as HLA-DRB1.67 Both conditions are linked to polymorphisms in IL-1β and TNF-α, as well as the presence of citrullinated proteins and RF.67 Furthermore, these diseases share a pathobiology characterised by elevated pro-inflammatory cytokines, reduced tissue inhibitors of metalloproteinases, increased MMPs and prostaglandin E2 (PGE2), all of which contribute to the tissue destruction observed in periodontitis and RA.68