Asthma: Pathophysiology, Triggers, and Clinical Hallmarks

Asthma is a heterogeneous chronic airway disease defined by:

• Variable respiratory symptoms (wheeze, cough, chest tightness, dyspnea)
• Variable expiratory airflow limitation (reversible spontaneously or with treatment)
• Airway inflammation (typically type 2: eosinophils, IL-4/5/13, FeNO↑)
• Bronchial hyperresponsiveness (exaggerated narrowing to triggers)

Common Triggers

Category	Examples
Allergens	Pollen, dust mite, pet dander, mold, cockroach
Irritants	Tobacco smoke, PM2.5, strong odors, cleaning chemicals, cold air
Infections	Rhinovirus, RSV, influenza
Exercise	Especially in cold/dry air (exercise-induced bronchoconstriction)
Emotions	Stress, laughter, crying (hyperventilation → airway drying)
Medications	ASA/NSAIDs (in aspirin-exacerbated respiratory disease), non-selective β-blockers
Comorbidities	GERD, rhinosinusitis, obesity, OSA

Diagnostic Cornerstones

• Spirometry: FEV₁/FVC < LLN + ≥12% and ≥200 mL FEV₁ improvement post-bronchodilator.
• Peak flow variability >20% (diurnal).
• FeNO >25 ppb (adults) supports type 2 inflammation.
• Bronchoprovocation (methacholine, mannitol) if spirometry normal but suspicion high.

Management follows GINA stepwise approach: ICS-formoterol as reliever (preferred) or SABA + maintenance ICS. Regular review, inhaler technique check, and written action plan are essential.