PRTN3 and rheumatoid arthritis: In contrast to RA, patients with SpA/PsA can have significant extra-articular disease associations (psoriasis, inflammatory bowel disease, uveitis).7 Furthermore, PsA is associated with increased body mass index in many patients with concomitant metabolic syndrome and cardiovascular morbidity.8 There are strong associations between seropositive (ACPA+) RA and cigarette smoking and HLADRB1 shared epitope alleles.3 9–12 These associations are not observed in seronegative RA.