Smoking and Interstitial Lung Disease

Cigarette smoking produces marked alterations in the lung parenchyma and in the population of immune and inflammatory cells present in the lower respiratory tract. These cigarette-induced changes appear to influence the incidence of two different interstitial lung diseases, histiocytosis X and sarcoidosis. Smoking is a strong risk factor for the development of pulmonary histiocytosis X, since the incidence of smoking is very high among patients with histiocytosis X: 90% of the patients with histiocytosis X were smokers; 46% of the controls were smokers (p less than .001). In contrast, smoking appears to reduce the incidence of sarcoidosis: 31% of the patients with sarcoidosis were smokers (p less than .05 compared to controls). In an effort to understand how cigarette smoking influences the incidence of these two disorders, we compared the numbers and types of immune and inflammatory cells recovered by bronchoalveolar lavage from nonsmoking and smoking controls and patients with histiocytosis X and sarcoidosis. Although nonsmoking patients with histiocytosis X did not have a significant increase in the number of alveolar macrophages recovered by lavage (p greater than .2 compared to normals), smoking patients had an increase in the number of alveolar macrophages similar to that observed in the control population. In contrast, the number of macrophages recovered from patients with sarcoidosis who smoked was considerably less than that observed in normal smokers (p less than .05 comparing patients with sarcoidosis and controls who smoked 1-20 cigarettes/day). This difference in the intensity of the cigarette-induced macrophage alveolitis observed in the two patient groups may be important in explaining the opposite effects of cigarette smoking on the incidence of histiocytosis X and sarcoidosis.