Defined as persistent productive cough for at least 3 consecutive months in at least 2 consecutive years
simple chronic bronchitis
chronic asthmatic bronchitis
chronic obstructive bronchitis
hypersecretion of mucus, beginning in the large airways is the hallmark of the disease
cigarette smoking, other air pollutants, such as sulfur dioxide and nitrogen dioxide are the major predisposing factors
Obstruction is explained by the "small airway disease," induced by goblet cell metaplasia with mucus plugging of the bronchiolar lumen; inflammation and bronchiolar wall fibrosis as well as coexistent emphysema.
Morphology in chronic bronchitis:
hypertrophy of mucous glands in the trachea and main-stem bronchi and a marked increase in mucin-secreting goblet cells in the surface epithelium
CD8+ T cells, macrophages, and neutrophils infiltration: in contrast to asthma, eosinophils are lacking
ratio of the thickness of the submucosal gland layer to that of the bronchial wall (Reid index; normally 0.4
neutrophilia increases markedly during bronchitic exacerbations
Chronic bronchiolitis (small airway disease), characterized by goblet cell metaplasia, mucus plugging, inflammation, and fibrosis
complete obliteration of the lumen due to fibrosis (bronchiolitis obliterans) may be seen in some.