The pathology of asthma, with special reference to changes in the bronchial mucosa.

The pathological features of 20 cases dying in status asthmaticus have been studied. In gross sections the lungs showed no emphysema, but mucus plugs in the air passages and focal areas of collapse were outstanding features. Five cases showed cystic bronchiectasis which was of a similar distribution to the focal areas of collapse, occurring in the upper lobes as commonly as in the lower lobes.Histologically, shedding of the ciliated bronchial mucosal cells was prominent and this is attributed to a transudation of oedema fluid from the submucosa. Areas of regeneration of the mucosa, with the presence of simple stratified epithelium, were seen frequently. The loss of the ciliated respiratory epithelium and the transudation of oedema fluid into the bronchial lumen, with interference with the action of the remaining ciliated cells, are considered to be the essential factors in the failure of clearance of the bronchial secretions in asthma. It is postulated that bronchospasm plays little or no part in the shedding of the bronchial mucosa or in the pathogenesis of the asthmatic attack.