Understanding Asthma: Causes and Effects

Oct 7, 2024

Lecture on Asthma

Introduction to Asthma

  • Chronic inflammatory condition of the respiratory passageways.
  • Causes narrowing of passageways, leading to difficulty breathing.
  • Can be fatal in extreme cases.

Etiology

  • Exact underlying causes not completely known.
  • Genetic Predisposition:
    • Associated with the Atopic Triad:
      • Asthma
      • Atopic Dermatitis (Eczema)
      • Allergic Rhinitis
    • Individuals may have a family history or underlying genes leading to hyper-responsiveness to allergens.
  • Samter's Triad:
    • Association with asthma, nasal polyps, and aspirin sensitivity.
    • Aspirin sensitivity causes an increase in leukotrienes due to inhibition of cyclooxygenase (COX) pathway, leading to bronchospasm.

Pathophysiology

  • Chronic Inflammatory Process:
    • Allergen exposure leads to activation of antigen-presenting cells like dendritic cells.
    • Dendritic cells present allergens to T-helper 2 (Th2) cells.
    • Th2 cells release interleukin-4 (IL-4) and interleukin-5 (IL-5).
      • IL-4 activates plasma cells to produce IgE antibodies.
      • IgE binds to mast cells, causing degranulation and release of histamines and leukotrienes.
      • IL-5 activates eosinophils, which release more leukotrienes and proteases.

Effects of Inflammatory Mediators

  • Bronchoconstriction:
    • Smooth muscle contraction leading to narrow airways.
  • Mucus Buildup:
    • Due to increased vascular permeability and inflammation.
  • Inflamed Mucosa:
    • Filled with fluid and inflammatory cells.

Chronic Changes

  • Asthma is reversible with treatment, but chronic exposure can lead to fibrosis and scarring.
  • Hygiene Hypothesis:
    • Suggests reduced pathogen exposure may lead to late-onset asthma due to impacts on immune maturation.

Exacerbating Factors

  • Allergens: Dust mites, pet dander, cockroaches.
  • Environmental: Cold air, exercise, viral infections (e.g., URIs), smoke inhalation.
  • Medications: Aspirin, beta blockers (due to inhibition of beta-2 receptors causing bronchoconstriction).

Additional Notes

  • Asthma symptoms can be triggered by multiple environmental and genetic factors.
  • Next steps involve diagnosing and distinguishing asthma from other conditions.
  • Stay tuned for more videos on diagnostics and protocol.