It is reported that, in CCP-2-positive patients with arthralgia, the ACPA profile did not differ between patients who evolved or not to overt arthritis, but patients recognizing two or more additional citrullinated peptides more frequently developed arthritis [21] and patients with undifferentiated arthritis who evolved to RA showed greater recognition of citrullinated peptides than those who did not [10]. Here, PRTN3 is linked to arthritic joint disease.