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Background: Asthma is a common respiratory disease caused by the interaction of genetic susceptibility and exposure to various environmental factors. Passive smoke exposure, characterized by parental smoking, has been shown to be a risk factor for the development of atopy and asthma.Objective: We sought to perform a genome-wide linkage screen for asthma and bronchial hyperresponsiveness (BHR) and to determine the influence of passive tobacco smoke exposure during childhood on the results of genetic linkage studies to investigate gene-environment interactions.Methods: A genome-wide linkage screen for asthma and BHR was performed in 200 families ascertained through a parent with asthma. Analyses were performed separately for the entire sample and for the smoking-exposed and nonexposed families.Results: For asthma and BHR, the strongest evidence for linkage was observed for chromosomes 3p and 5q. The families in which the children were exposed to passive smoking accounted for the evidence for linkage of BHR to 5q (P Conclusion: The results from this study demonstrate that the influence of susceptibility genes for a common disease such as asthma might not be apparent unless there is the appropriate exposure to environmental stimuli, such as passive exposure to cigarette smoke. This approach should be useful for identification of asthma susceptibility genes.

Background Asthma is a complex genetic disease characterized by reversible intermittent airway obstruction and respiratory symptoms primarily caused by acute and chronic bronchial inflammation. Recently, a gene potentially involved in airway remodeling, a disintegrin and metalloprotease 33 (ADAM33) , was implicated in asthma susceptibility. Objective We sought to determine whether polymorphisms in ADAM33 are associated with asthma or closely related phenotypes in 4 different asthma populations. Methods Eight single nucleotide polymorphisms (SNPs) were evaluated in the 3′ portion of ADAM33 in 4 unique asthma populations (African American, US white, US Hispanic, and Dutch white). These SNPs were previously reported to be associated with asthma in white populations from the United States and United Kingdom. Results Significant associations were observed with at least one SNP and asthma in each population ( P = .0009–.04). Related phenotypes that included total serum IgE levels and skin test responsiveness were also associated ( P = .003–.05). However, no single SNP was associated across all populations. Additionally, haplotype analysis revealed that no single haplotype accounted for asthma susceptibility risk, although potential risk haplotypes existed within some of the populations. Conclusion Replication of the original ADAM33 findings in these 4 additional asthma populations suggests that this gene (and perhaps others that interact with it) is important in the development and pathogenesis of asthma.