Inflammatory Arthritis in Systemic Sclerosis: Its Epidemiology, Associations, and Morbidity

Objective: To describe the epidemiology, associations, and impact of inflammatory arthritis (IA) in systemic sclerosis (SSc). Methods: Patients with SSc prospectively enrolled in the Australian Scleroderma Cohort Study were included. IA was defined clinically as the presence of synovitis on examination. Logistic regression was used to determine the associations of IA with SSc manifestations and serological parameters. Patient-reported outcome measures were used to capture physical function and health-related quality of life (HRQoL). Results: IA was a common SSc manifestation affecting one-third (33.3%) of patients over a median follow-up of 4.3 (1.7–8.4) years. Associations of IA included diffuse SSc (odds ratio [OR] 1.33, 95% confidence interval [95% CI] 1.01–1.74, P = 0.042), concurrent musculoskeletal manifestations (joint contractures and tendon friction rubs, OR 1.70, 95% CI 1.34–2.15, P < 0.001); myositis (OR 2.11, 95% CI 1.39–3.20, P < 0.001), and sicca symptoms (OR 1.57, 95% CI 1.14–2.16, P = 0.006), whereas IA was negatively associated with pulmonary arterial hypertension (OR 0.52, 95% CI 0.35–0.78, P = 0.002). Neither the presence of rheumatoid factor nor U1 small nuclear RNP were associated with IA (OR 1.13, 95% CI 0.88–1.44, P = 0.331, OR 1.46, 95% CI 0.89–2.39, P = 0.129 respectively). Positive anticyclic citrullinated protein antibodies, although at low frequency, were more common in those with IA compared with those without IA (7.5% vs 1.5%, P < 0.001). IA was associated with significantly lower HRQoL score (P < 0.001) and more physical disability than in those without IA (P < 0.001). Conclusion: IA is a common disease manifestation that is more frquently seen in diffuse disease. IA is associated with poor HRQoL and physical disability. Further research is needed into the effective management of IA in SSc.