Nesse W et al. – Within the periodontal stroma, citrullination is an inflammation–depended process. In periodontal epithelium, citrullination is a physiological process. Additional citrullinated proteins are formed in periodontitis, apparently similar to those formed in RA–affected synovial tissue. Periodontitis induced citrullination may play a role in the aetiology of rheumatoid arthritis.