Asthma: Pathological Essentials
Asthma is a chronic inflammatory disorder of the airways characterized by reversible bronchoconstriction, airway hyper-responsiveness, and mucus production.
1. Pathogenesis: The Allergic Reaction
- Atopic (Extrinsic): Type I hypersensitivity (IgE-mediated). Triggered by environmental allergens. Often associated with eczema or allergic rhinitis.
- Non-atopic (Intrinsic): Triggered by non-immune stimuli such as cold air, exercise, or viral infections.
2. Morphological Hallmarks
| Finding | Description |
|---|---|
| Curschmann spirals | Spiral-shaped mucus plugs containing shed epithelium. |
| Charcot-Leyden crystals | Eosinophil-derived crystalline aggregates (galectin-10). |
| Airway Remodeling | Thickened basement membrane, smooth muscle hypertrophy, and goblet cell hyperplasia. |
3. Exam Must-Knows
- Airway Obstruction: FEV1/FVC ratio is decreased, but unlike COPD, this is significantly reversible with bronchodilators (e.g., albuterol).
- Triggers: Look for associations with the “atopic triad”: asthma, allergic rhinitis, and atopic dermatitis.
- Aspirin-Induced Asthma: A clinical triad of nasal polyps, asthma, and aspirin sensitivity. Caused by inhibition of COX, shunting arachidonic acid toward the leukotriene pathway.
Pathology Pearl: The histology of asthma is dominated by eosinophilic infiltration. The thickening of the basement membrane and airway remodeling are hallmarks of chronic, persistent disease.