Definition: an acute or chronic disorder characterized by widespread and largely reversible reduction in the caliber of bronchi and bronchioles, due in varying degrees to smooth muscle spasm, mucosal edema, and excessive mucus in the lumens of airways. Cardinal symptoms are dyspnea, wheezing, and cough. Attacks or exacerbations may be induced by airborne allergens (molds, pollens, animal dander, dust mite and cockroach antigens), inhaled irritants (cold air, cigarette smoke, ozone), physical exercise, respiratory infection, psychological stress, or other factors. The signs and symptoms of bronchial asthma are caused by the local release of spasmogens and inflammatory mediators (histamines, leukotrienes, prostaglandins) and other substances from mast cells, eosinophils, lymphocytes, neutrophils, and epithelial cells. Airway caliber may be abruptly and drastically reduced during a paroxysm or after diagnostic challenge with methacholine or histamine, and may quickly return to normal after administration of a bronchodilator (inhaled β-adrenergic agonist or subcutaneous epinephrine).
Synonym(s): reactive airway disease
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