Asthma and atopy – a total genome scan for susceptibility genes

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Abstract
Background:  Allergic asthma is an increasingly common disease of complex inheritance. Several studies have suggested candidate regions, but genetic heterogeneity, ethnic differences and varying study designs may in part explain the lack of identified and confirmed susceptibility genes. Investigation of different populations will further clarify the topic. We therefore evaluated allergic asthma and increased total and specific IgE in 39, 45 and 57 sib‐pairs from 100 Danish allergy families. Methods:  Affected sib‐pairs meeting a narrow phenotype definition were selected for the three phenotypes atopy, allergic asthma and increased total IgE. We performed a total genome scan using 446 microsatellite markers and obtained nonparametric linkage results from the MAPMAKER/SIBS computer program. Results:  Our study revealed four candidate regions (MLS > 2) on chromosome 1p36, 3q21–q22, 5q31 and 6p24–p22, and 15 candidate regions (1 < MLS < 2) that may contain susceptibility genes for asthma and atopy. We did not find linkage to the candidate genes TNF‐β, FcER1β and Il4R‐α, except for weak support for linkage of the asthma phenotype to TNF‐β (MLS = 1.18). Conclusions:  We found evidence for two new asthma and atopy loci, 1p36 and 3q21–q22, and supported linkage in the Danish population to seven previously reported candidate regions.