PRTN3 and rheumatoid arthritis: A hallmark feature of RA is the abnormal production of autoantibodies including rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPAs) which are detectable up to 10 years before symptoms of arthritis develop.23 This stage of the disease is termed “preclinical RA” as ACPA seropositivity does not always lead to joint disease.24 RF was the first autoantibody identified in patients with RA and targets the Fc portion of IgG.