PRTN3 and rheumatoid arthritis: The prevalence of PD is increased approximately twofold in RA,1–3 and severity correlates with measures of disease severity in RA and anticitrullinated protein/peptide antibodies (ACPA).4 In addition, the demonstration of autoantibodies to RA-associated autoantigens in patients with PD5 supports the hypothesis that PD may drive the autoimmunity that antedates the onset of RA.