What is bronchiectasis, a chronic respiratory condition often affecting older adults with a history of respiratory infections or conditions like cystic fibrosis?

What is Bronchiectasis?

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

Core Pathophysiology

The disease involves a self-perpetuating "vicious cycle" where chronic bacterial infection triggers airway inflammation, which impairs mucociliary clearance, leading to further infection and progressive structural lung damage. 1 This cycle is mediated by:

• Neutrophils, T lymphocytes, and monocyte-derived cytokines that release inflammatory mediators 1
• Elastase and collagenase that destroy the elastic and muscular components of bronchial walls 1
• Recurrent bacterial colonization that perpetuates ongoing airway injury 1

Cardinal Clinical Features

The hallmark symptom is chronic productive cough with sputum production, though some patients may present with nonproductive cough. 1 Additional manifestations include:

• Recurrent respiratory infections that define clinically significant disease 1
• Dyspnea and breathlessness as common symptoms 1
• Hemoptysis (coughing up blood) 1
• Rhinosinusitis, fatigue, and thoracic pain 1

Diagnostic Criteria

Clinically significant bronchiectasis requires BOTH radiological evidence AND clinical symptoms. 1 Specifically:

• High-resolution CT (HRCT) scanning is the diagnostic procedure of choice, with sensitivity and specificity exceeding 90% 1
• Radiological bronchiectasis alone without symptoms does not constitute disease requiring treatment, particularly in asymptomatic elderly individuals 1

Common Underlying Causes

While historically considered post-infectious, an increasing proportion of patients now have identifiable underlying disorders due to improved childhood infection treatment with antibiotics and immunizations. 1 Major causes include:

Focal/Localized Distribution 1

• Bronchial obstruction (foreign body, tumor, broncholithiasis, lymph node compression)
• Previous pneumonia or tuberculosis

Diffuse Distribution 1

• Cystic fibrosis (most common identifiable cause in developed countries)
• Immunodeficiency states (congenital/acquired hypogammaglobulinemia, HIV infection)
• Primary ciliary dyskinesia
• Allergic bronchopulmonary aspergillosis (ABPA)
• Chronic Mycobacterium avium complex (MAC) infection
• Connective tissue diseases (rheumatoid arthritis, inflammatory bowel disease)
• Congenital disorders (α1-antitrypsin deficiency, tracheobronchomegaly, cartilage deficiency syndromes)

Epidemiology and Disease Burden

Prevalence has increased substantially worldwide over recent decades, with U.S. estimates of approximately 139 per 100,000 individuals. 1 The disease causes:

• Quality of life impairment equivalent to severe COPD based on St. George's Respiratory Questionnaire scores 1
• Significant morbidity and mortality burden requiring comprehensive management 1

Important Clinical Distinction

Traction bronchiectasis is a distinct entity caused by contractile forces from surrounding fibrotic lung tissue pulling on adjacent bronchi, occurring in the context of interstitial lung diseases like idiopathic pulmonary fibrosis. 2 This represents a different pathophysiologic mechanism and is not addressed by standard bronchiectasis management guidelines. 2

Key Clinical Pitfall

Do not confuse radiological bronchiectasis with clinically significant disease. Asymptomatic bronchial dilation on CT, particularly in elderly patients or those with interstitial lung disease, does not warrant bronchiectasis-specific treatment unless accompanied by the clinical syndrome of cough, sputum production, and/or recurrent infections. 1