Cast bronchitis in infants and children.

Seventy-two children (age range, 3 months to 5.5 years) with a clinical diagnosis of obstructive bronchitis (asthmatoid or spastic bronchitis or bronchiolitis) were found to have bronchial casts in the gastric fluid, and in 2 additional cases casts were spontaneously expectorated in the bronchial exudate. Cast bronchitis had a long-term course of 10 to 24 months in 65 of the 74 patients. Common radiologic findings included bronchi presumably filled with secretions, areas of atelectasis, and lung emphysema of varying degrees. Cast bronchitis did not appear to be associated with eosinophilia and elevated serum IgE levels. Therefore, an extrinsic allergic mechanism is not likely involved in the pathogenesis of the condition. Bronchial casts had varying consistencies; although they were usually soft, they were sometimes rather hard. They were hollow, often ramified, and white and measured from 0.5 to 2 cm in length. Histologically, they consisted of metaplastic squamous epithelium with a varying degree of inflammatory cells and noncellular material. Some differences in biochemical composition were observed between bronchial casts and bronchial exudate of acute catarrhal bronchitis. No viruses could be isolated in 11 cast specimens. Our results suggest that cast formation is mainly related to the metaplastic transformation of the bronchial epithelium and that this metaplasia may play an important pathophysiologic role in certain infants and children with obstructive bronchitis.