[Bronchial hyperreactivity other than that seen in asthma].

Although generally associated with asthma, bronchial hyper-responsiveness has been observed in several clinical situations. Indeed, it has been clearly shown that patients with allergic rhinitis exhibit frequently bronchial hyperresponsiveness. The latter may be an important factor in the development of chronic airway obstruction. Airway hyperresponsiveness to direct bronchoconstrictors, histamine and metacholine, is seen also in subjects with chronic airflow limitation. Several lines of reasoning suggest that this may be different than the airway hyperresponsiveness seen in asthmatics and may predominantly relate to the degree of airflow obstruction. Consequently, in the presence of resting airflow obstruction, histamine and metacholine tests are difficult to interpret vis-a-vis a diagnosis of asthma. Some studies suggest accelerated decline of lung function in subjects with chronic airflow limitation and airway hyperresponsiveness. In interstitial lung disease preliminary data form subjects with lung diseases localized to the pulmonary interstitium suggest no (or very little) tendency to airway hyperresponsiveness. However, more data are necessary. Subjects with bilateral lung transplantation appear to develop mild, generally asymptomatic airway hyperresponsiveness which has been suggested to be due to cholinergic denervation hyper-sensitivity. Finally, asthmatics and nonasthmatics both may develop increased degrees of airway responsiveness following viral respiratory tract infections. Virus-induced airway inflammation is likely important in the pathogenesis of asthma in some subjects.