COPD: Pathological Essentials
COPD is a chronic, progressive airflow obstruction that is not fully reversible. It encompasses two primary, often overlapping, disease processes: Chronic Bronchitis and Emphysema.
1. Comparison: Chronic Bronchitis vs. Emphysema
| Feature | Chronic Bronchitis | Emphysema |
|---|---|---|
| Pathology | Mucus gland hypertrophy/hyperplasia. | Destruction of alveolar walls. |
| Reid Index | Increased (>0.4). | Normal. |
| Clinical Phenotype | Blue Bloater (cyanosis, edema). | Pink Puffer (pursed lips, cachectic). |
2. Emphysema Subtypes
- Centriacinar: Most common; affects the respiratory bronchioles. Strongly associated with smoking; predominant in the upper lobes.
- Panacinar: Affects both alveoli and respiratory bronchioles. Associated with Alpha-1 Antitrypsin (AAT) deficiency; predominant in the lower lobes.
3. Exam Must-Knows
- AAT Deficiency: Classic cause of early-onset emphysema in a non-smoker. Liver involvement is also common (PAS-positive globules in hepatocytes).
- Mechanism of Damage: Protease-antiprotease imbalance (neutrophil elastase activity is unchecked).
- Spirometry: Decreased FEV1/FVC ratio (<0.7) and increased Total Lung Capacity (TLC).
Pathology Pearl: Chronic bronchitis is defined clinically as a persistent productive cough for at least 3 months in at least 2 consecutive years.