Asthma

Disease / Phenomenon

Asthma is a chronic disease of the airways in which the bronchial tubes are persistently inflamed and abnormally twitchy, narrowing sharply in response to triggers that healthy airways tolerate without difficulty. Attacks bring wheezing, chest tightness, coughing — often worse at night or early morning — and breathlessness, caused by the combination of smooth muscle constriction, mucosal swelling, and thick mucus plugging. Between episodes many people feel entirely well, which is part of what makes the condition easy to underestimate. Common triggers include allergens such as dust mite, pollen, mold, and animal dander, as well as respiratory viruses, cold air, exercise, tobacco smoke, air pollution, and occupational irritants.

Asthma is now understood as several overlapping biological endotypes rather than one disease. The most studied is type 2 inflammation, driven by IL-4, IL-5, and IL-13 acting through Th2 cells and innate lymphoid cells, recruiting eosinophils, driving IgE production and mast cell degranulation, and stimulating goblet cell mucus secretion. Non-type-2 asthma involves neutrophilic and IL-17-associated inflammation. Sustained inflammation produces airway remodeling: basement membrane thickening, smooth muscle hypertrophy, and fibrosis. This page separates these processes, traces their molecular pathways, and lists the biomarkers that measure them.