Asthma

Asthma is a chronic inflammatory airway disease characterized by:

• Reversible airflow obstruction
• Airway hyperresponsiveness
• Chronic airway inflammation

It is driven by immune-mediated and inflammatory pathways.

Core mechanisms:

• Th2-mediated inflammation
• Eosinophilic airway infiltration
• Mast cell activation
• Leukotriene production
• Airway smooth muscle hyperreactivity

Key mediators:

• Histamine
• Leukotrienes (LTC4, LTD4, LTE4)
• IL-4, IL-5, IL-13

See:

• Type I Hypersensitivity
• Leukotriene Pathway

Result:

• Bronchoconstriction
• Mucus hypersecretion
• Airway edema
• Chronic airway remodeling (untreated disease)

• Episodic wheezing
• Shortness of breath
• Chest tightness
• Cough (often nocturnal)
• Reversible obstruction on spirometry

Diagnosis supported by:

• ↓ FEV1/FVC
• Improvement after bronchodilator

Mechanism:

Acute bronchospasm + airway inflammation.

First-line treatment:

• Albuterol (SABA)

Severe exacerbation:

• Systemic Corticosteroids –> prednisone
• Oxygen
• Consider epinephrine in severe cases

Steroids reduce inflammation but do NOT provide immediate bronchodilation.

• As-needed low-dose ICS-formoterol

OR

• SABA PRN (less preferred in modern guidelines)

• Daily low-dose Inhaled Corticosteroid

OR

• As-needed ICS-formoterol

Consider:

• Montelukast (alternative)

• Low or medium-dose ICS + LABA
• SMART therapy (ICS-formoterol maintenance and reliever)

• High-dose ICS + LABA
• Add-on therapies:
  1. Leukotriene modifiers
  2. Anti-IgE (omalizumab)
  3. Anti-IL-5 biologics
• Consider systemic corticosteroids

Bronchodilators:

• Short-Acting Beta Agonists (SABA)
• Long-Acting Beta Agonists (LABA)

Anti-inflammatory:

• Inhaled Corticosteroids
• Leukotriene Modifiers
• Biologic agents (severe disease)

Mechanism:

COX inhibition → shunting toward leukotriene pathway → bronchospasm.

Often responds well to:

• Montelukast
• Zileuton

• Status asthmaticus
• Airway remodeling
• Frequent hospitalizations
• Respiratory failure (severe cases)

• Asthma is primarily an inflammatory disease, not just bronchospasm.
• Inhaled corticosteroids are foundational therapy.
• Leukotrienes are potent bronchoconstrictors.
• SABA overuse increases mortality risk.
• Steroids treat inflammation, beta-agonists treat bronchospasm.
• Always assess control before escalating therapy.

• Leukotriene Modifiers
• Corticosteroids
• Histamine & Antihistamines
• Type I Hypersensitivity