PRTN3 and rheumatoid arthritis: This is indicated by the presence of autoantibodies against citrullinated peptides (ACPA) and rheumatoid factor (RF), which can be accompanied with arthralgia.3 4 Of all those at risk of developing RA (RA-risk), only 30% of individuals4, 6 go on to develop the disease within 2 years suggesting there are additional (environmental) factors5 and genetic predispositions7, 9 that may drive progression to clinical arthritis.