Lung function abnormalities in different connective tissue diseases.

Lung volumes, forced expiratory flow-volume curves, diffusing capacity indexes, and arterial blood gases were measured in 72 non-smoking patients with various connective tissue diseases (13 with rheumatoid arthritis, 17 with systemic lupus erythematosus, 25 with progressive systemic sclerosis, 10 with primary Sjögren's syndrome, 4 with polymyositis, and 3 with mixed connective tissue disease). Small airways disease and a diffusion capacity impairment were the most frequent and marked functional abnormalities in the whole group, and were often present in asymptomatic patients. Different lung function defects seemed to be present in each disease group. In fact, large airway obstruction was prevalent in progressive systemic sclerosis, diffusion capacity impairment in systemic lupus erythematosus, and small airways disease in rheumatoid arthritis. In contrast, primary Sjögren's syndrome appeared to be the connective tissue disease in which lung function abnormalities were less frequent and less pronounced.