Association of FcεR1‐β polymorphisms with asthma and associated traits in Australian asthmatic families

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Abstract
Asthma is a genetically complex disease, and is characterized by elevated serum immunoglobulin E (IgE) levels, elevated blood eosinophil counts and increased airway responsiveness. Polymorphisms in the β subunit of the high affinity receptor for IgE (FcεR1-β) have been previously associated with these phenotypes and with an increased risk of asthma. To investigate the association of all known bi-allelic polymorphisms in FcεR1-β to asthma and quantitative traits associated with asthma in a selected sample of Australian asthmatic children and their nuclear families. Australian Caucasian nuclear families (n = 134 subjects) were recruited on the basis of a child proband with current, severe, symptomatic asthma. The quantitative traits assessed included serum levels of total IgE and specific IgE to house dust mite and mixed grass, blood eosinophil counts and the dose–response slope of the forced expiratory volume in 1 s to histamine provocation. Neither the Leu181 nor the E237G mutations were detected in this population. Allele B of RsaI intron 2 (RsaI_in2*B) was significantly associated with physician-diagnosed asthma (ever) (P = 0.002). Alleles of both the RsaI_in2 and RsaI exon 7 (RsaI_ex7) polymorphisms were significantly associated with loge total serum IgE levels and the combined RAST index. RsaI_ex7 was also associated with loge blood eosinophil counts. These associations were independent of age, sex and familial correlations. This study supports a role for the FcεR1-β gene or a nearby gene in the pathogenesis of asthma.