Asthma

Abstract

Asthma is one of the most common chronic diseases, with an estimated 300 million people affected worldwide [ 1 ]. The incidence of asthma continues to increase, especially among children. Asthmais defi ned by its clinical, physiological, and pathological characteristics [ 1 ]. Its predominant clinical feature is recurrent episodes of wheezing, breathlessness, chest tightness, and coughing, particularly at night or in the early morning. The main physiological feature is episodic obstructed breathing characterized by constricted expiratory airways, leading to asthma’s clinical features.The dominant pathological feature is chronic infl ammation of the airways associated with airway hyperresponsiveness, which obstructs or limits airfl ow when airways are exposed to various risk factors.Chronic inflammation is characterized as infi ltration of infl ammatory cells (e.g., mast cells, eosinophils, and T cells; see chapter “ Overview ” under the part “Immune system”) and is sometimes associated with airway structural changes called “remodeling”such as mucus hyperproduction by epithelial cells, subepithelial fi brosis by fi broblasts, hypertrophy and/or hyperplasia of airway smooth muscle cells, and proliferation of blood vessels.