A and B viruses, parainfluenza virus, respiratory syncytial virus, coxsackievirus A21, rhinovirus, and the viruses that cause rubella and measles. Mycoplasma pneumoniae, Bordetella pertussis, and Chlamydia pneumoniae also cause acute infectious bronchitis, often in young adults. Malnutrition and exposure to air pollutants are predisposing or contributory factors. Bronchitis often recurs in patients with chronic bronchopulmonary diseases that impair bronchial clearance mechanisms and may recur in those with chronic sinusitis, bronchiectasis, bronchopulmonary allergy, or COPD and in children with hypertrophied tonsils and adenoids. Cough-variant asthma, in which the degree of bronchoconstriction is not sufficient to produce overt wheezing, may be caused by allergen inhalation in an atopic person or chronic exposure to an irritant in a person with relatively mild airway hyperreactivity.
Management is similar to that of ordinary asthma.
Pathology and Pathophysiology Hyperemia of the mucous membranes is the earliest change, followed by desquamation, edema, leukocytic infiltration of the submucosa, and production of sticky or mucopurulent exudate. The protective functions of bronchial cilia, phagocytes, and lymphatics are disturbed, and bacteria may invade the normally sterile bronchi, with consequent accumulation of cellular debris and mucopurulent exudate. Cough is essential to eliminate bronchial secretions. Airway obstruction may result from edema of the bronchial walls, retained secretions, and, in some cases, spasm of bronchial muscles. Onset of a distressing cough usually signals onset of bronchitis.