Polyarthritis in primary Sjögren's syndrome represents a distinct subset with less pronounced B cell proliferation a Dutch cohort with long-term follow-up.

The primary goal was to investigate the differences in patients with and without polyarthritis (PA) in primary Sjögren's syndrome (pSS) in a clinical-based (real-life) setting, with respect to demographic characteristics, cumulative prevalence of other extra-glandular manifestations (EGM), hypergammaglobulinaemia and serological profile. The secondary goal was to describe the characteristics of polyarthritis in our pSS cohort. Patients diagnosed with pSS and polyarthritis but without rheumatoid arthritis (RA)-like changes on X-rays were followed up prospectively from June 1991 until August 2014, with at least one check-up each year. Patients fulfilling the criteria for concomitant connective tissue disorders were excluded. Data were collected with respect to the prevalence of systemic auto-antibodies (anti-nuclear antibodies (ANA), anti-Sjögren's syndrome-related antigen A (anti-SSA), anti-Sjögren's syndrome type B (anti-SSB) and immunoglobulin M-rheumatoid factor (IgM-RF)) and other EGM related to pSS. A total of 134 patients were included for the final analysis. The median follow-up was 86 months (range 0-368 months). Twenty-two patients (16.4 %) had polyarthritis. The prevalence of systemic auto-antibodies including rheumatoid factor did not differ between the two groups. Anti-cyclic citrullinated peptide (CCP) occurred much more frequently in the polyarthritis-positive (PA+) patients (13.7 vs 0.9 %; p = 0.015). Hypergammaglobulinaemia (p = 0.002) and increased levels of IgG (p = 0.013) occurred much less frequently in the PA+ group compared to the polyarthritis-negative (PA-) group. The mean total number of EGM or of any specific EGM did not differ between the two groups. Most patients had a mild, symmetrical PA predominantly involving the finger joints (proximal interphalangeal joints/metacarpophalangeal joints (PIP/MCP)) and/or wrists and/or metatarsophalangeal (MTP) joints. Significant morning stiffness lasting ≥1 h was found infrequently (32 %). All patients were treated with a classic (c) disease-modifying antirheumatic drug (DMARD), but in two cases, treatment was necessary with a tumour necrosis factor (TNF) inhibitor. PA+ pSS patients are more frequently anti-CCP positive and have a less pronounced B cell proliferation than PA- patients. PSS patients with PA seem to have a relatively mild articular expression with a favourable course.