From a better knowledge of periodontal disease to Porphyromonas gingivalis target for rheumatoid arthritis disease activity.

Periodontal disease (PD) and rheumatoid arthritis (RA) are both inflammatory diseases affecting the tooth and joint, with local inflammation associated with bone loss. Bacterial infections by oral bacteria are involved in periodontal inflammation, and the best known to be associated with PD is Porphyromonas gingivalis (Pg). A large body of recent data suggests a strong involvement of this specific bacteria, Pg, in PD outcomes, but also in RA. The aim of this review is to discuss the association between PD and Pg, RA and its mechanisms, and to determine whether targeting Pg bacteria could improve RA. Numerous epidemiological studies have already confirmed the association between PD and Pg, as well as between PD and RA, which is mainly associated with a common genetic background, the shared epitope. The involvement of Pg in pathogenesis of RA is supported by the induction of gingival citrullinated proteins and therefore of anti-citrullinated proteins antibodies, which constitute the most specific biomarker of RA. The prevalence of Pg in RA is still controversial, but studies should include patients with preclinical and early RA. Finally, recent data confirmed that targeting Pg is highly effective in improving RA.