Pulmonary Involvement in Primary Sjögren’s Syndrome: Interstitial Lung Disease Phenotypes and Diagnostic Challenges

Pulmonary involvement in primary Sjögren’s syndrome (pSS) is common and exhibits significant clinical heterogeneity, particularly in cases where interstitial lung disease (pSS-ILD) develops. Reported variability in prevalence, radiologic phenotypes, and clinical outcomes indicates both underlying biological diversity and differences in classification criteria, case ascertainment, and diagnostic approaches. Pulmonary manifestations may be subclinical, and early interstitial abnormalities are frequently undetected due to the limited sensitivity of chest radiography. Presentations such as ILD-first or non-sicca onset, seronegative disease, and coexisting or mimicking conditions, including lymphoproliferative disorders and amyloidosis, increase the difficulty of diagnosis. High-resolution computed tomography (HRCT) demonstrates a wide range of patterns, including inflammatory, fibrotic, and mixed phenotypes, which often overlap and change over time. Reliance on pattern-based categorization may not adequately reflect the underlying pathobiology; for example, those with usual interstitial pneumonia (UIP)-like morphology have significant prognostic implications within the pSS spectrum. A structured, multidomain assessment that integrates symptoms, pulmonary function, and HRCT findings, ideally inside a multidisciplinary discussion (MDD), may boost diagnostic accuracy and risk stratification. Nevertheless, heterogeneity in definitions and reporting continues to impede comparability across patient cohorts. Additional research is necessary to standardize phenotyping frameworks and identify predictors of disease progression to inform individualized diagnostic and management strategies.