Ultrastructure of airways in children with asthma

Abstract

The histopathology and ultrastructure of bronchial mucosa in lung biopsies from 2 children with bronchial asthma in remission were studied, and they were compared with lung samples from 2 children who died in status asthmaticus. Light microscopy of all samples showed changes typical of bronchial asthma, e.g., mucus plugging, goblet cell hyperplasia, thickening of bronchial basement membrane, peribronchial smooth smooth muscle hypertrophy and eosinophilic infiltration. EM revealed that the mucus plugs consisted of moderately electron-dense floccular material containing degenerate epithelial cells, macrophages and cell fragments. The luminal surfaces of ciliated cells showed cytoplasmic blebs and abnormal cilia. Mast cells in various stages of degranulation were scattered between bronchial epithelial cells. The subepithelial hyaline layer, commonly referred to as thickened basement membrane, consisted of collagen fibrils in plexiform arrangement. The basement membrane proper appeared intact. These EM changes, particularly the presence of mast cells and subepithelial collagen deposits, were also found in autopsy samples. Marked, possibly irreversible changes may be present in the lungs of patients with severe bronchial asthma, even when they are asymptomatic. These pulmonary changes could be the direct consequence of mast cell activation and the release of various mediators. No evidence of immune complex deposition was found.