Genetic factors in childhood asthma.

The prevalences of asthma and atopy were examined in the families of 77 asthmatic and 87 control children attending a London general practice. The prevalence of asthma in first degree relatives of asthmatic children was found to be significantly higher than in relatives of control children, and this difference was more pronounced for relatives of atopic probands than for relatives of non-atopic probands. Among the relatives of asthmatics, atopic asthma was more common than non-atopic asthma, irrespective of the atopic status of the proband. However, among the relatives of control children, neither the prevalence of asthma nor the atopic status of the asthmatic relatives was influenced by the atopic status of the proband. These findings support the hypothesis that asthma and atopy are inherited independently. Although atopy itself does not predispose to asthma, it may enhance a genetic susceptibility to the condition, thus increasing the likelihood that the latter will be expressed.