Bronchiectasis Definition
Bronchiectasis is a chronic respiratory disease characterized by permanent, irreversible dilation of the bronchi with destruction of the elastic and muscular components of their walls, typically resulting from acute or chronic infection. 1, 2
Core Pathophysiologic Features
Bronchiectasis requires both radiological confirmation (permanent bronchial dilation on CT scan) and clinical symptoms for diagnosis. 2 The condition involves:
- Permanent structural damage to bronchial walls with loss of elastic and muscular tissue, distinguishing it from reversible bronchial dilation 1
- Abnormal bronchial widening visible on high-resolution CT (HRCT) scanning, which is the diagnostic gold standard 1
- Chronic inflammatory cycle involving recurrent bacterial infection, neutrophilic inflammation, impaired mucociliary clearance, and progressive structural lung damage 1
Cardinal Clinical Presentation
The hallmark symptoms include:
- Chronic productive cough with purulent sputum production as the most characteristic feature 1
- Recurrent respiratory infections due to impaired airway clearance mechanisms 2
- Dyspnea and fatigue affecting more than 60% of patients daily 3
- Hemoptysis and digital clubbing in some cases 2
Distinction from Cystic Fibrosis
The term "bronchiectasis" generally refers to non-cystic fibrosis bronchiectasis, explicitly excluding patients with cystic fibrosis despite similar radiological and clinical features. 1 This distinction is critical as management strategies differ significantly between the two conditions.
Underlying Etiologies
With increased antibiotic use in developed countries, an increasing proportion of bronchiectasis cases now have identifiable underlying disorders rather than post-infectious causes. 1 Common predisposing conditions include:
- Focal causes: Bronchial obstruction from foreign bodies, tumors, or broncholithiasis 1
- Diffuse causes: Cystic fibrosis, immunodeficiencies (particularly IgG deficiencies), HIV infection, primary ciliary dyskinesia, allergic bronchopulmonary aspergillosis, and chronic Mycobacterium avium complex infection 1, 2
- Idiopathic or post-infective cases remain common, particularly in regions with high tuberculosis prevalence 1
Pathophysiologic Vicious Cycle
The disease perpetuates through a self-reinforcing cycle where chronic bacterial colonization triggers neutrophilic inflammation, which releases elastase and collagenase that destroy bronchial walls, further impairing mucociliary clearance and promoting more infection. 1 This cycle explains the progressive nature of untreated disease and guides therapeutic interventions aimed at breaking this pattern.
Clinical Significance
Bronchiectasis causes significant morbidity and mortality, with disease burden equivalent to severe COPD and up to 30% mortality at 1-year follow-up after exacerbations. 2 The prevalence has increased worldwide, with recent UK data showing rates of 566/100,000 in adult women and 486/100,000 in adult men 1