Airway inflammation and remodeling in asthma : current concepts.

Asthma is a heterogeneous disorder of the airways with intermittent airflow obstruction frequently accompanied by increased responsiveness of the bronchi to a wide variety of exogenous and endogenous stimuli. A number of different types of asthma have been described, based largely on the clinical manifestations of, or factors precipitating, the airflow obstruction. As the disease becomes more severe and chronic, it is suggested that the airflow obstruction may progressively lose some of its reversibility and, in this respect, resemble some aspects of chronic obstructive pulmonary disease (COPD). However, in a small proportion of patients with life-threatening asthma, the airways are highly labile on account of greatly enhanced bronchial hyperresponsiveness. At the other end of the disease severity spectrum there are many patients with mild intermittent asthma whose disease only manifests when exposed to particular sensitizing allergens to which they are sensitive (e.g. outdoor allergens during the pollen season).