Respiratory involvement in patients with Sjögren's syndrome: is it a problem?

We examined the pulmonary involvement in 40 patients with primary Sjögren's syndrome (1 degree SS), and 26 patients with secondary SS (2 degrees SS) and compared them with 100 healthy matched controls, 40 patients with rheumatoid arthritis (RA) without evidence of SS and 30 patients with scleroderma. The respiratory evaluation included questionnaire, physical examination, chest roentgenogram and pulmonary function studies (spirometry, flow/volume curve, total lung capacity and diffusion: DLCO). The most common symptom in 1 degree SS was dyspnea (25%). Xerotrachea was present only in 1 degree SS (12.5%) while pleurisy only in 2 degrees SS and RA (7.7% and 2.5% respectively). The most common functional defect in 1 degree SS was interstitial lung disease (30%) and in 2 degrees SS and RA airways obstruction (46% and 32.5% respectively). Finally, small airways disease was frequent in all patient groups, as well as the control group. Comparison between patients with glandular and extraglandular SS revealed that xerotrachea was a manifestation of glandular and diffuse interstitial lung disease of extraglandular SS. Finally, comparison of patient groups and controls revealed statistical significant differences in: FVC and DLCO between extraglandular 1 degree SS/controls, FEV1/FVC ratio between 2 degrees SS/controls and the same between RA/controls, FVC, TLC, DLCO between scleroderma/controls, DLCO between scleroderma/SS and separately between scleroderma/1 degree SS and scleroderma/extraglandular 1 degree SS (which were the subgroups of SS with lowest DLCO). Diffusion impairment correlated with the presence of cryoglobulins and low complement levels, suggesting immune complex deposition as a mechanism of the interstitial lung disease.(ABSTRACT TRUNCATED AT 250 WORDS)