[Interstitial lung disease in patients with connective tissue diseases]

Interstitial lung disease is a significant prognostic factor in connective tissue diseases. To further clarify clinical and immunological features of interstitial lung disease, we studied 894 consecutive patients with connective tissue diseases first evaluated between 1970 and 1993. Interstitial lung disease was found in 101 of 181 (56%) patients with systemic sclerosis, 92 of 183 (50%) with overlap syndrome, 35 of 76 (46%) with polymyositis/dermatomyositis, and 13 of 444 (3%) with systemic lupus erythematosus (p < 0.05, systemic lupus erythematosus vs. other connective tissue diseases). The presence of interstitial lung disease correlated with decreased survival in systemic sclerosis and in polymyositis/dermatomyositis, but not in overlap syndrome or in systemic lupus erythematosus. Interstitial lung disease in patients with connective tissue diseases was classified into two types: acute (n = 8) and chronic (n = 233). Among the 8 patients with acute disease, 4 (all with dermatomyositis) died of respiratory failure and 3 (all with systemic lupus erythematosus) responded to corticosteroids. Among the 233 patients with chronic interstitial lung disease, 20 had polymyositis/dermatomyositis with anti-aminoacyl tRNA synthetase antibodies and 40 had overlap syndrome with anti-U1 RNP antibodies. Respiratory failure in these patients was not frequent and occurred late in the course of the disease. As a cause of death, respiratory failure was associated with autoantibodies to topoisomerase I and aminoacyl tRNA synthetase but not anti-U1 RNP. Autoantibodies to aminoacyl tRNA synthetases were detected before the development of interstitial lung disease in 9 patients with polymyositis/dermatomyositis. We conclude that the clinical features of interstitial lung disease associated with connective tissue diseases vary with the type of connective tissue disease, and that analysis of autoantibodies can be useful in establishing a diagnosis and in forecasting the course and outcome.