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Asthma is a chronic inflammatory airway disease characterized by variable airflow obstruction, bronchial hyperresponsiveness, and symptoms of wheezing, dyspnea, chest tightness, and cough. It affects over 300 million people worldwide and is the most common chronic disease in children.
Asthma pathophysiology involves type 2 airway inflammation driven by mast cells, eosinophils, and Th2 lymphocytes responding to allergens, irritants, or respiratory viruses. Mediator release (histamine, leukotrienes, prostaglandins) causes bronchospasm, mucosal edema, and mucus hypersecretion. Bronchial hyperresponsiveness amplifies responses to stimuli. Chronic inflammation causes airway remodeling — subepithelial fibrosis and smooth muscle hypertrophy — that contributes to fixed airflow limitation in severe disease.
Clinical reasoning distinguishes asthma from other causes of wheezing: COPD (older, smoker, fixed obstruction), vocal cord dysfunction (inspiratory stridor, normal spirometry), cardiac wheezing ('cardiac asthma'). GINA guidelines classify severity and guide stepwise therapy. Inhaled corticosteroids are the cornerstone of persistent asthma management. Acute exacerbation severity is assessed by PEFR, accessory muscle use, and oxygen saturation. Life-threatening features — silent chest, altered consciousness, bradycardia — require immediate intubation preparation alongside maximal bronchodilator and steroid therapy.