PRTN3 and rheumatoid arthritis: Rheumatoid arthritis (RA), which affects 0.1%–2.0% of adults in industrialized countries, is an autoimmune, inflammatory, and multisystem disorder characterized by chronic synovitis, systemic inflammation, and autoantibodies, particularly including the rheumatoid factor (RF) and anti-citrullinated peptide antibody (ACPA) (1).