Exercise-induced bronchial lability in wheezy children and their families.

Studies have been caried out to investigate bronchial lability as assessed by means of standardized running exercise tests. It was found that children who had been wheezy as infants had an abnormal degree of bronchial lability, even if they were asymptomatic, and closely resembled children who had continued to wheeze. The relatives of asthmatic children displayed a high incidence of bronchial lability, atopic diseases, and positive skin tests, and a similar incidence was found in the relatives of babies with wheezy bronchitis. The difference from a control population was particularly noticeable in the healthy relatives of wheezy children. Studies in monozygotic twins have shown a very high incidence of concordance for asthma, particularly when bronchial lability is taken into account. These studies suggest a common genetic basis for wheezing in childhood, based on the inheritance of bronchial lability. The difference in responses of the actively asthmatic subject from that of other labile subjects suggests that additional environmental factors are necessary to interact with the inherited bronchial lability.