No linkage or association of five polymorphisms in the interleukin-4 receptor α gene with atopic asthma in Italian families

The literature contains conflicting reports on the association of common variants of the interleukin (IL)-4 receptor alpha (IL4RA) gene with atopic asthma. The purpose of the present study was to investigate the linkage and association of several gene polymorphisms with atopic asthma in a large series of well-characterized individuals. Analysis of five polymorphisms (150V, E375A, C406R, S478P and Q551R) of the IL4RA gene was performed in 823 individuals from 182 families with atopic asthmatic children from north-east Italy. The subjects were tested for clinical asthma, total serum IgE level, skin prick test positivity to common aeroallergens, and bronchial hyperresponsiveness to methacholine. The frequency of the polymorphisms was similar to that reported for other populations. The 375, 406, 478 and 551 polymorphisms were in linkage disequilibrium, as previously reported. No linkage or transmission disequilibrium was observed in the families between any mutation and any of the phenotypes investigated. No multipoint haplotype was associated with any phenotype. In conclusion, the IL4RA gene does not seem to play an important role in genetic predisposition to atopic asthma in the population tested.