Overview
Definition
A heterogeneous disease characterized by chronic airway inflammation and a history of respiratory symptoms that vary over time and in intensity, together with variable expiratory airflow limitation.
Epidemiology
Affects ~260 million people globally. Common in childhood but can develop at any age.
Etiology & Risk Factors
- Genetic predisposition (atopy)
- Environmental triggers (allergens, viral infections, cold air, exercise)
- Type 2 inflammation (eosinophilic) or non-Type 2
Clinical Symptoms
- Wheezing
- Shortness of breath
- Chest tightness
- Cough (often worse at night or early morning)
Clinical Approach
Diagnosis
- Spirometry showing obstructive pattern (FEV1/FVC < 0.70) with reversibility (>12% and 200mL increase in FEV1 after bronchodilator)
- Methacholine challenge test (if spirometry is normal but clinical suspicion is high)
Management
- Inhaled Corticosteroids (ICS) - Foundation of therapy
- ICS-Formoterol (MART therapy) for both maintenance and reliever
- Short-Acting Beta Agonists (SABA) for acute relief
- Biologics (Omalizumab, Mepolizumab) for severe eosinophilic/allergic asthma
Complications
- Status asthmaticus
- Airway remodeling
- Respiratory failure
- Pneumothorax