The pieces of evidence pointing in this direction include association with radiological damage of RA, which is independent of the ACPA status [4,7]; detection of anti-CarP antibodies in blood samples taken before the onset of clinical symptoms of RA [5–8]; and experiments in mice showing that immunization with cabamylated peptides was able to elicit erosive arthritis [14]. Here, PRTN3 is linked to arthritic joint disease.