An electron-microscopic study of the airways in patients with farmer's lung.

By electron-microscopy, we have shown that airway epithelial changes occur in farmer's lung, at a level which is even as high as the carina of the right upper lobe. When spores were apparent in the bronchial lumen, ciliated and goblet cells had disappeared, and in some specimens, even basal cell layers. In general, the ciliated cells were those most affected; the cell destruction is that of bronchitis, with the cilia being less affected than the rest of the ciliated cell. Ciliogenesis is stimulated but it does not keep pace with the cell destruction, which advances more rapidly. Disturbed ciliogenesis is suggested. The pathogenesis of epithelial damage is obscure. By reason of epithelial damage, it is suggested that the superficial afferent nerves in the bronchial epithelium are susceptible to irritation; degranulating mast cells in the vicinity of the epithelial nerves may also be involved in the bronchial hyperreactivity observed in some patients. Mast cells were found in the alveoli; these might influence alveolar ventilation. The alveoli presented granulomas characteristic of farmer's lung.