Bronchioles may be involved by inflammation and scarring as either an isolated or focal condition (e.g., a scarred bronchiole from a prior focal infection) or as a widespread or diffuse process. Inflammation and scarring of bronchiolar walls and the adjacent alveolar septa may be accompanied by metaplasia of the bronchiolar or alveolar epithelium. The bronchiolar epithelium may undergo goblet-cell metaplasia or squamous metaplasia. The metaplasia on the surface of adjacent fibrotic alveoli may take the form of bronchiolar epithelium, goblet-cell metaplasia, or squamous metaplasia. The appearance of bronchiolar-type epithelium on the surface of fibrotic alveoli next to a scarred bronchiole is sometimes called lambertosis, which refers to an older concept that this epithelium grew onto the alveolar surface from the bronchiolar lumen via the canals of Lambert.

Some of the diseases that may involve bronchioles with inflammation and possibly scarring include bronchopneumonia (see Chapter 61), organizing pneumonia (formerly known as bronchiolitis obliterans organizing pneumonia; see Chapter 62), constrictive bronchiolitis (see Chapter 63), respiratory and membranous bronchiolitis due to tobacco smoke (see Chapter 64), follicular bronchiolitis (see Chapter 65), diffuse panbronchiolitis (see Chapter 66), and small airway reactions to inorganic dust exposures (see Chapter 67). Histopathologic clues to the cause of bronchiolar scarring may be found in some cases (e.g., pigment-laden macrophages in respiratory bronchiolitis or foreign-body giant cells in chronic aspiration).