PRTN3 and rheumatoid arthritis: As ACPA is highly specific (Schellekens et al., 2000), detectable early and predictive of rapid progression and erosion of RA (Nielen et al., 2004; Ronnelid et al., 2005; Syversen et al., 2008; Rombouts et al., 2015), individuals with ACPA positivity are at increased risk for RA, especially those with arthralgia (van de Stadt et al., 2011).