In addition, as the prevalence of RA-related auto-antibodies in the general population increases with increasing age, we hypothesized that patients with RA presenting at older age are more often rheumatoid factor (RF)-positive or anti-citrullinated peptide antibodies (ACPA)-positive and therefore have more severe disease [8, 11–13, 15–20]. The gene discussed is PRTN3; the disease is rheumatoid arthritis.