How do the Two Types of Asthma differ in Pathogenesis, Onset, Triggers, and Treatment?

Overview:

• A chronic inflammatory disease affecting approximately 25.7 million people in the US.
• In Canada, the affected population is roughly estimated by dividing the US figure by 10, due to population differences.
• Characterized by bronchiole obstruction leading to bouts of severe respiratory attacks.
• Importantly, these attacks are reversible with proper management and treatment.

Pathophysiology of Asthma:

• Involves airway obstruction caused by inflammatory processes and bronchospasm.
• Two main pathways lead to these attacks:
  1. Hypersensitivity reactions
  2. Hyper-responsive reactions

Types of Asthma Based on Onset and Triggers:

1. Extrinsic Asthma (Allergic Asthma):

   • Usually begins in childhood.
   • Caused by a type I hypersensitivity reaction (allergic reaction).
   • Triggered by inhaled antigens/allergens (e.g., pollen, dust mites).
   • The immune response involves an exaggerated allergic reaction similar to those seen in allergy or hay fever.
   • Family history of allergies and atopy (inherited genetic predisposition) is common, so it is sometimes called Atopic Asthma.

2. Intrinsic Asthma (Non-allergic or Adult-Onset Asthma):

   • Develops later in life, often in adulthood.
   • The triggers and underlying mechanisms differ from extrinsic asthma.
   • The bronchial tissues become hyper-responsive without a clear allergic trigger.
   • Triggers include:
     • Respiratory infections (viral or bacterial)
     • Stress
     • Exposure to cold air or environmental irritants (smoke, pollutants)
     • Exercise, especially in cold or dry conditions
     • Certain drugs or medications

Intrinsic Asthma – Possible Causes

• Cause: is idiopathic, though there is evidence that the following may be pre-disposing factors:
  • Cold weather or cold inhalation causing airway irritation.
  • Viral or bacterial respiratory infections leading to airway hyper-responsiveness.
  • Exposure to cigarette smoke or environmental pollutants.
  • Exercise-induced bronchospasm, especially with cold or dry air.
  • Drug reactions or sensitivities.

Emerging Research & Outgrowing Asthma:

• Some recent studies suggest that individuals can “outgrow” asthma.
• Possible explanations include:
  • Desensitization to triggers: Similar to allergy desensitization protocols (e.g., allergy shots), gradual exposure might reduce sensitivity.
  • Reduction in immune response: The immune system might become less reactive over time.
• Caution: Such desensitization should only be undertaken under medical supervision to avoid severe reactions like anaphylaxis.

Summary:

• Asthma involves episodic airway obstruction due to inflammation and bronchospasm, with triggers varying depending on the type.
• Managing triggers and controlling inflammation are key to preventing attacks and reducing collateral damage from repeated inflammatory episodes.
• Both types demonstrate the importance of understanding individual triggers for effective management.
• New research indicates some individuals may outgrow asthma through natural desensitization, but this must be managed carefully under medical guidance.