Clinical and Demographic Predictors of Loss of Pulmonary Function in Systemic Sclerosis

The course of functional pulmonary involvement in systemic sclerosis remains controversial; and it is not known if specific clinical or demographic features are predictive of subsequent changes in pulmonary function. To address these questions, we conducted a non-concurrent prospective study of serial pulmonary function in 24 patients with systemic sclerosis unselected for pulmonary involvement over a mean follow-up interval of 59.7 months. Initial values for the entire group demonstrated a mild restrictive defect with a mild reduction in gas exchange. Although a restrictive pattern was most common, normal and obstructed pulmonary function were seen. Mean rates of change of FVC, TLC, FEV1/FVC, and Dco for the entire group were not different from normal, but substantial variability in the course of pulmonary functional involvement was seen among individuals. Changes in gas transfer, lung volumes, and airflow can occur independent of each other. Rates of change in pulmonary function were not predicted by initial pulmonary function, race, sex, duration of disease, cardiac involvement, roentgenographic fibrosis, or regression of skin disease. Patients with severe Raynaud' phenomenon exhibited the greatest fall in Dco over time, suggesting an association between peripheral and pulmonary vascular involvement. A correlation between exertional dyspnea and rapid loss of Dco was noted. Former smokers had significantly greater rates of loss of FVC and Dco than either non-smokers or current smokers, suggesting that cessation of smoking was a response to rapidly declining function in a subgroup of susceptible smokers. We detected a wide spectrum of severity of pulmonary prognosis in systemic sclerosis, ranging from normal pulmonary function to rapidly progressive disease leading to death. This study indicates that patients with prolonged survival do not necessarily have a rapidly progressive pulmonary component, but those with severe Raynaud's phenomenon and susceptible smokers are at very high risk for rapid deterioration of pulmonary function.