Complement Consumption as a Predictor of Pulmonary Manifestation in Patients with Primary Sjögren’s Syndrome: Results from a Unicentric Observational Study

Background/Purpose: Primary Sjögren’s syndrome (pSS) may present with respiratory manifestations ranging from proximal and distal airways impairment to various forms of interstitial lung disease (pSS-ILD), which can affect up to 16% of patients¹. Studies on factors associated with pulmonary manifestations of pSS are few and of heterogeneous results^2,3,4. Our main objective was to identify clinical and laboratory elements related to pSS that may be predictors of lung disease.

Methods: Retrospective study of pSS patients in follow-up at a university hospital. Patients older than 18 years who met pSS classificatory criteria according to the American-European Consensus of 2002 were included. Patients with other CTD were excluded. Epidemiological, clinical, and laboratory data were extracted from medical records. Chest CT scans were reviewed by a radiologist without knowledge of the patients’ clinical data. Data from patients with pSS with and without pulmonary manifestations were compared and Fischer’s test was applied for statistical evaluation.

Results: Seventy patients with pSS were selected (68% female and mean age 45.8 ± 9.5). Fifteen (21.4%) had some form of pulmonary manifestation, 14 (20%) of ILD and 1 of bronchiolitis (1.4%). Among the analyzed variables, a statistically significant association was found between complement consumption (C3 or C4) and presence of pulmonary manifestation (38.4% versus 10.2%; p: 0.02). No association was found between autoantibodies such as ANA, RF, Ro/SSA and La/SSB or other forms of extraglandular manifestation (Table 1). No variables were correlated with the presence of pulmonary cysts or pSS-ILD. The radiological findings of patients with pulmonary manifestations are summarized in Table 2.

Conclusion: In our series of patients with pSS, we found a high frequency of individuals with pSS and pulmonary impairment. Complement consumption was a predictor of this form of manifestation, an association never seen before.