Interstitial Lung Disease Phenotypes and Predictive Risk Factors in Primary Sjögren's Syndrome

Background/Objectives: The prevalence of Interstitial Lung Disease (ILD) and risk factors for its development in patients with primary Sjögren's syndrome (pSS) are still debated, possibly due to the existence of heterogeneous pSS-related ILD phenotypes. The aims of this study were: 1. To investigate the prevalence and predictive factors for ILD development in a single-center pSS cohort; 2. To characterize different pSS-ILD phenotypes. Methods: Clinical, laboratory and imaging data of pSS patients attending our center from January 2019 to September 2023 were retrospectively analyzed. ILD presence was confirmed on HRCT. Results: Forty-three out of 474 enrolled pSS patients presented ILD (M:F = 6:37), accounting for an overall ILD prevalence of 9.1%. In 19 cases, ILD was the first manifestation of pSS (ILD-onset), while in 24 ILD was diagnosed after pSS (ILD-incident). Compared to ILD-onset, ILD-incident patients more often presented pSS-related hematologic abnormalities (p = 0.012), cutaneous involvement (p = 0.027), inflammatory arthralgias (p = 0.026), C4 hypocomplementemia (p = 0.012) and positive RF (p = 0.031). On the other hand, ILD-onset patients were significantly older at pSS diagnosis (p = 0.008) and presented more severe fibrosis on HRCT (p = 0.008). On the univariate analysis, higher ESSDAI (p = 0.011), Raynaud's phenomenon (p = 0.009), anti-Ro52 (p = 0.031), hypergammaglobulinemia (p = 0.011), Rheumatoid Factor (RF) (p = 0.038) and C4 hypocomplementemia (p = 0.044) at baseline were associated to ILD development during follow-up. On the multivariate analysis, the ESSDAI at baseline (p = 0.05) and Raynaud's phenomenon (p = 0.013) at baseline were the only independent predictors of ILD development. Conclusions: ILD is a relatively common and clinically heterogenous pSS manifestation. Elevated disease activity at pSS onset is a risk factor for ILD development, prompting careful follow-up and intriguingly suggesting that immunomodulatory therapies may prevent ILD.