A familial predisposition in bronchial hyperresponsiveness among patients with allergic rhinitis

Background: Nonasthmatic subjects with allergic rhinitis often have bronchi al hyperresponsiveness (BHR). The mechanisms responsible for ERR in asthma include genetic predisposition and airway inflammation, but the causes of B HR in allergic rhinitis are poorly understood. Objective: The aim of this study was to investigate whether there is a fami lial prediposition in allergic rhinitis-associated BHR. Methods: One hundred fifteen children with allergic rhinitis (probands) and their family members underwent methacholine bronchial challenge and skin p rick tests with airborne allergens. The probands were divided into 2 groups : BHR(+) (methacholine PC20 <18 mg/mL determined by the dosimeter method; n = 42) and BHR(-) (n = 73). Results: The overall prevalence of BHR was higher in family members of BHR( +) probands than in those of BHR(-) probands (23.3% [27 of 116] vs 10.5% [2 1 of 200], P < .01). In mothers, this difference was marked (21.4% vs 8.2%, P < .05); a similar trend was observed in fathers (16.7% vs 6.8%) and sibl ings (34.4% vs 18.5%), although the differences did not reach significance (.05 < P < .1). The bronchial responsiveness index (BR index), a continuous variable derived from the results of methacholine challenge, was significa ntly higher among family members of the BHR(+) group than those of the BHR( -) group. Furthermore, even when only family members without BHR were consi dered, the BR index was significantly higher among those (n = 89) of the BH R(+) group than those (n = 179) of the BHR(-) group. There was no differenc e in atopic status as assessed by the prevalence of atopy (or atopy index) between family members of the BHR(+) group and the BHR(-) group. Conclusion: Our results indicated that there is a significant familial pred isposition for BHR among patients with allergic rhinitis. Further studies a re needed to elucidate whether genetic factors play a role in allergic rhin itis-associated BHR.