In a previous study pulmonary hyperinflation was observed frequently in patients with primary Sjogren's syndrome (pSS) and elevated serum beta-2 microglobulin (beta2m) concentrations were associated with hyperinflation.
To evaluate the significance of baseline serum beta2m concentration and to identify other possible risk factors for pulmonary involvement in long-term follow-up of patients with pSS.
Nineteen pSS patients whose pulmonary function tests (PFTs) had been previously studied were reexamined after a median follow-up of 10 years. Pulmonary symptoms were recorded, chest radiograph, and high-resolution computed tomography (HRCT) were evaluated and methacholine provocation and PFTs including flow-volume spirometry, body plethysmography, and diffusing capacity performed.
Baseline serum beta2m concentrations correlated inversely with follow-up total lung capacity (TLC), vital capacity (VC), and diffusing capacity (DL), and positively with residual volume (RV), all expressed as percentage of predicted values. Diminished airways resistance (Raw) and, correspondingly, elevated specific conductance (SGaw) were frequent findings in pSS patients at follow-up, indirectly implying stiffness of the lungs and a restrictive decrease in lung volumes. Baseline serum protein concentration was higher and IgG concentration tended to be higher in pSS patients who at follow-up had elevated SGaw compared with others. Interstitial changes in HRCT were found more frequently in patients with elevated SGaw than in those without.
Our results suggest that subtle restrictive changes in pulmonary function are more prone to develop in the long term in pSS patients with elevated serum beta2m concentration and other signs of immunological activity at baseline.