A familial predisposition in bronchial hyperresponsiveness among patients with allergic rhinitis.

BACKGROUND: Nonasthmatic subjects with allergic rhinitis often have bronchial hyperresponsiveness (BHR). The mechanisms responsible for BHR in asthma include genetic predisposition and airway inflammation, but the causes of BHR in allergic rhinitis are poorly understood.

OBJECTIVE: The aim of this study was to investigate whether there is a familial predisposition in allergic rhinitis-associated BHR.

METHODS: One hundred fifteen children with allergic rhinitis (probands) and their family members underwent methacholine bronchial challenge and skin prick 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% [21 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 siblings (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 significantly higher among family members of the BHR(+) group than those of the BHR(-) group. Furthermore, even when only family members without BHR were considered, the BR index was significantly higher among those (n = 89) of the BHR(+) group than those (n = 179) of the BHR(-) group. There was no difference 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 predisposition for BHR among patients with allergic rhinitis. Further studies are needed to elucidate whether genetic factors play a role in allergic rhinitis-associated BHR.