reactive airway disease
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Asthma is a common disorder, with a prevalence of about 5% in the U.S., and a leading cause of illness and disability in people between 2 and 17 years of age. It is responsible for 14.5 million outpatient visits and 5,000 deaths yearly in this country. The prevalence of asthma has been increasing during the past 25 years, particularly in children under age 5. Asthma first occurring in childhood is more likely to be allergic in origin and to show seasonal variation. Chronic sinusitis and gastroesophageal reflux disease are statistically correlated with asthma. A subset of people with allergic asthma also have nasal polyps and sensitivity to aspirin and other nonsteroidal antiinflammatory drugs (Samter triad). Occupational exposure to airborne irritants or allergens causes at least 10% of chronic asthma in adults. Current views of the pathophysiology of asthma emphasize its inflammatory component and the risk of gradual, irreversible airway remodeling due to subepithelial fibrosis in poorly controlled asthma. Interleukin 13 has been implicated as a mediator of such fibrosis, and the presence of antibody to Chlamydia pneumoniae has been linked statistically to accelerated deterioration of lung function in patients with asthma. Current recommendations for treatment of chronic or severe asthma call for use of antiinflammatory drugs (particularly inhaled corticosteroids). Other treatments include β2-adrenergic bronchodilators (albuterol, terbutaline, salmeterol), xanthines (theophylline, oxtriphylline, dyphylline), mast cell stabilizers (cromolyn, nedocromil), and antileukotrienes (montelukast, zafirlukast, zileuton). Self-monitoring of peak respiratory flow rate with a simple portable device helps patients adjust drug doses for optimal effect. Avoidance of allergens, irritants, and other known triggers is essential to good control.