ABSTRACT
OBJECTIVE: To evaluate the clinical, serologic, and MHC class II antigen characteristics of a group of patients with primary Sjögren's syndrome (SS) and severe arthritis. METHODS: A case-control study comparing 35 patients with primary SS: 17 with inflammatory arthritis, 18 without arthritis. RESULTS: All patients fulfilled criteria for primary SS. There were no demographic or clinical features other than inflammatory arthritis, often erosive, that distinguished patients with arthritis from those without. All patients had anti-Ro/SSA autoantibodies, most had anti-La/SSB autoantibodies, and a high percentage of these patients had anti-citrullinated peptide antibodies absent in those without inflammatory arthritis. HLA typing revealed that most patients with anti-citrulline antibodies expressed MHC class II molecules with the shared epitope (SE). The presence of DRB1*0301 linked to the expression of anti-Ro/SSA autoantibodies did not influence the level or frequency of anti-citrulline antibodies in these patients. CONCLUSION: Severe arthritis with features resembling rheumatoid arthritis including erosive disease can occur in primary SS, particularly among those with anti-citrulline antibodies and the SE.