Background Primary Sjögren (pSS) is a chronic inflammatory autoimmune disease characterised by lymphocytic infiltration of the exocrine glands. Most patients present Keratoconjuntivitis sicca and xerostomia, and about 40% of them develop musculoskeletal manifestations, the most common being arthralgia and intermittent non-erosive polyarthropathy involving mainly the small joints. Rheumatoid factor (RF) is positive in more than 50% of p-SS patients, but cyclic citrullinated peptide antibodies (anti-CCP) are positive in less than 10% of cases. In rheumatoid arthritis (RA) presence and titre of anti-CCP have been related to the presence of shared epitope (SE). There are no available data in pSS.
Objectives To describe the prevalence of arthritis in a large cohort of patients with pSS, and to investigate whether a relationship exists between the presence of arthritis and positive RF, positive anti-CCP or SE.
Methods All patients diagnosed as having pSS at our Center between January 1988 and December 2010 who fulfilled the American-European Consensus Group diagnostic criteria were included. Levels of IgM RF >30 UI/mL and IgG anti-CCP >10 UI/mL were considered positive. HLA typing for the MHC class I and II was determined. Standard radiographs of hands and feet were reviewed to evaluate the presence of bone erosions, by three rheumatologists.
Results 250 pSS patients were included. The prevalence of arthritis was of 26.8%. RF and anti-CCP were determined in all cases. Hands and feet x-ray of were performed in all patients with arthritis and in all patients with positive anti-CCP. The MHC class I and II were determined in 43 patients. RF was positive in 115 (46%) cases and anti-CCP in 9 (3.6%). Seven of the 9 patients with positive anti-CCP suffered arthritis and 3 developed radiographic bone erosions after a long follow-up. The MHC class II antigen DRB1* 01 01 (SE) was present in all 3 cases.
Conclusions Almost a quarter of patients with pSS develop arthritis that usually is non-erosive and mainly involves small joints. The picture may mimic RA as more than 50% of patients with pSS are RF-positive. Anti-CCP antibodies are present in 10-12% of pSS patients and seem to be closely associated with the presence of arthritis. However, anti-CCP could not be employed as a predictor of future progress to RA. In these cases presence of SE may suggest a real overlap syndrome between pSS and RA and not a misdiagnosed RA.
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Disclosure of Interest None Declared