The detection of Rheumatoid Factor (RF) and Anti-Citrullinated Peptide Antibodies (ACPA) shows good sensitivity and specificity in the early diagnosis of RA, but autoantibodies may share epitopes, and some non-RA rheumatic diseases or chronic infections may also present with positive RF or anti-CCP antibodies (Taylor et al., 2011). Here, PRTN3 is linked to rheumatoid arthritis.