Initially it was thought that the obvious pathophysiological link between RA and citrullinated peptides leading to formation of antibodies was the apparent cause of the clinical manifestations, but soon it was demonstrated that there were groups of patients with clinical manifestations of RA that did not had anti-CCP antibodies so its genesis was not explained by citrullination. Then it is possible a diversity of antigens exposed during the illness and perhaps different clinical presentations associated with each one or its combinations. So actually, some studies are attempting to show other possible antigens involved in RA and one of them uses homocitrulline as an antigenic basis to RA pathophysiology. The carbamylation or homocitrullination is a posttranslational modification of proteins that occurs when the amino acid lysine reacts with cyanate in a non-enzyme-mediated process generating homocitrulline. Mydel, Bokarewa and cols. demonstrated that immunization of mice with homocitrulline- and citrulline-containing peptides leads to development of erosive arthritis following intra-articular injection of homocitrulline-containing peptides and proposed that homocitrulline induced activation of T cells is a key mechanism in the pathogenesis of autoimmune arthritis as it serves as an initial triggering event for neo-epitope recognition of citrulline containing peptides. Recently It has been shown that rheumatoid arthritis patients has homocitrullinated proteins in his joints which can trigger an inflammatory response with formation of antibodies against homocitrulline.