Histopathologic features of early and progressive asthma.

During the last decade, morphologic studies on bronchial biopsy specimens have led to our present understanding of asthma as an inflammatory airways disease. However, little knowledge exists about the sequence of cellular events during the disease or of possible mucosal changes early in asthma. So far the primary cause, the site of damage, and the mechanisms inducing the inflammatory reaction remain to be elucidated. A multifactorial genetic susceptibility may be important for the development of asthma. Suggested factors that may trigger changes in the cells' morphologic and functional phenotype are viral infections, allergen exposure, maternal factors, diet, and smoking. Current evidence has implied that interactions between epithelial cells and the subepithelial connective tissue in the mucosa are important for normal homeostatic balance. Changes in airway epithelial phenotype possibly resulting from altered gene expression in its lining cells may be very important even as a first line change in asthma.