Sjögren's Syndrome is Rare in Psoriasis, but Common in Psoriatic Arthritis: Two Sides of a Coin - A Single Centre Retrospective Study.

Background: Sjögren's syndrome (SS) may accompany psoriatic arthritis (PsA), if ever, and its presence during psoriasis (PsO) is rare. Recent observations of an association with predominantly axial forms of PsA are intriguing. Whether SS complicates PsO and PsA to the same extent is not known. Objectives: To investigate the frequency of SS in patients with PsO and PsA, and elucidate disease features associated with SS. Methods: In this retrospective analysis, we collected the data about previously recorded in the follow-up files of PsO and PsA patients. We classified patients who met the 2002 American-European Sjögren's syndrome Consensus Group Criteria (AECG) or the 2016 ACR-EULAR Classification Criteria for primary Sjögren's Syndrome as SS. Frequency rates of SS in PsA patients and in PsO patients without arthritis were compared and SS characteristics were described. Results: Of the 184 PsO patients, 112 had PsA and 72 PsO alone. A substantial proportion of PsA patients had SS. This association was not present in the PsO group (PsA: 20(%17.9), PsO: 0(%0), p<0.001). Gender distribution, mean age, and PsO onset age were similar in both. Symmetric polyarticular involvement was rare, and most PsO patients with arthritis were ANA positive at a serum dilution level of 1:320 and beyond. Conclusions: SS seems to be part of the clinical picture in a substantial proportion of PsA patients, and its absence in PsO implies that SS may be arthritis associated. Whether the type of arthritis is critical in developing SS in PsA deserves further studies with large populations.