This study provides some novel insights into the diagnostic value of antibodies to acetylated epitopes that have only recently been described to occur in patients with RA.10,18 They were found mostly in ACPA positive patients and partially cross-react with ACPA and/or anti-CarP antibodies.22,33,34 Nevertheless, AAPA and other AMPAs may also be present in a subgroup of seronegative patients, indicating that they might have added diagnostic value for reducing the serological gap. The gene discussed is PRTN3; the disease is rheumatoid arthritis.