Mucin production and peribronchial fibrosis was observed after AF challenge but there was no difference to WT controlsPeriostin deficient mice had increased AHR and serum IgE levels following allergen challenge versus WTPeriostin deficient mice had blunted TGF‐β responses to allergen, which affected differentiation of Treg cellsPeriostin's role in the airway was to regulate AHR and allergen induced IgE. The gene discussed is AHR; the disease is atrial fibrillation.