The etiology and control of bronchial hyperresponsiveness in children

Bronchial hyperresponsiveness (BHR) describes the exaggerated bronchoconstrictor response to a host of stimuli such as cold air or exercise that occurs in most patients with asthma. It is an important feature of asthma because BHR correlates with diurnal peak expiratory flow variation, bronchospasm following exercise, the need for asthma medications, and asthma severity. Many studies published in the past year have increased our understanding of BHR. First, epidemiologic studies have revealed BHR to be a risk factor for the subsequent development of asthma. BHR is also more common in children than adults, and the persistence of BHR is related to atopy. Second, genetic and pathophysiologic studies have improved our understanding of the etiology of BHR. The genetic basis for BHR, atopy, and asthma was further elucidated with the finding of a cluster of potential candidate genes for asthma susceptibility on chromosome 5. In addition, eosinophilic infiltration and basement membrane thickening of the airways, both characteristic findings noted in patients with asthma, were found to correlate with pulmonary function and degree of BHR. Lastly, studies on treatment of BHR confirmed the beneficial effects of inhaled glucocorticoid therapy and allergen avoidance on BHR in children with asthma. In addition, a new type of asthma medication, the leukotriene inhibitors, has been shown to decrease BHR in adults with asthma and may eventually prove to be an effective medication for children with chronic asthma.