What are the causes of cystic bronchiectasis?

Causes of Cystic Bronchiectasis

Cystic bronchiectasis is primarily caused by underlying disorders that predispose patients to chronic or recurrent infections, including cystic fibrosis, immunodeficiencies, primary ciliary dyskinesia, allergic bronchopulmonary aspergillosis (ABPA), and chronic Mycobacterium avium complex (MAC) infection. 1

Primary Causes of Cystic Bronchiectasis

Genetic Disorders

• Cystic fibrosis is one of the most common identifiable causes of bronchiectasis in the United States and Europe, occurring in 1 per 2,000-3,000 live births, caused by mutation of the gene encoding the CF transmembrane regulator protein 2
• Primary ciliary dyskinesia is a genetic disorder affecting ciliary structure and function, leading to impaired mucociliary clearance and recurrent sinopulmonary infections 2
• Alpha-1-antitrypsin deficiency can predispose to the development of bronchiectasis 1
• Connective tissue disorders like Ehlers-Danlos Syndrome and Marfan syndrome can cause bronchiectasis due to weakened bronchial walls with reduced structural integrity 3

Immune-Mediated Disorders

• Allergic bronchopulmonary aspergillosis (ABPA) causes central cystic bronchiectasis (inner two-thirds of chest on CT scan) due to immune-mediated inflammation in response to Aspergillus fumigatus 2
• Rheumatoid arthritis is associated with bronchiectasis in 2-5% of cases 3
• Inflammatory bowel disease can predispose to bronchiectasis development 1

Immunodeficiency States

• Congenital and acquired hypogammaglobulinemia (especially IgG and/or IgG subclasses) 1
• Common variable immunodeficiency 4
• HIV infection 1

Infectious Causes

• Chronic Mycobacterium avium complex (MAC) infection, particularly in white women in their seventh or eighth decade 2
• Prior severe pneumonia or tuberculosis 1, 4
• Recurrent bacterial infections leading to progressive airway injury 1

Focal Causes

• Bronchial obstruction by foreign bodies, tumors, broncholithiasis, or compression by peribronchial lymph nodes 1
• Post-pneumonia focal damage 1

Other Causes

• Tracheobronchomegaly (Mounier-Kuhn syndrome) 1
• Cartilage deficiency (Williams-Campbell syndrome) 1
• Yellow nail syndrome 1
• Aspiration or toxic inhalation 1
• Idiopathic (up to 38% of cases have no identifiable cause) 4

Pathophysiology of Cystic Bronchiectasis

• Bronchiectasis involves a vicious cycle of chronic bronchial infection, inflammation, impaired mucociliary clearance, and structural lung damage 5
• Recurrent bacterial colonization and infection lead to progressive airway injury mediated by neutrophils, T lymphocytes, and monocyte-derived cytokines 1
• Inflammatory mediators, elastase, and collagenase cause destruction of the elastic and muscular components of bronchial walls 1
• The contractile force of surrounding lung tissue exerts traction, expanding the diameter of involved airways 1
• Increased bronchial arterial proliferation and arteriovenous malformations can predispose to recurrent hemoptysis 1

Diagnostic Approach

• High-resolution CT scanning is the diagnostic procedure of choice to confirm bronchiectasis, with sensitivity and specificity exceeding 90% 2
• Key features on HRCT include enlarged internal bronchial diameter, failure of larger airways to taper while progressing to the lung periphery, and air-fluid levels in dilated airways 2
• Cystic bronchiectasis appears as cluster of cysts or grape-like structures on imaging 6
• Location-based patterns can help identify specific causes:
  • Upper lobe distribution: cystic fibrosis, ABPA, traction bronchiectasis from tuberculosis or sarcoidosis 6
  • Lower lobe distribution: chronic aspiration, hypogammaglobulinemia, primary ciliary dyskinesia 6
  • Right middle lobe and lingula: atypical mycobacterial infections, primary ciliary dyskinesia 6
  • Central distribution: often seen in ABPA 2

Clinical Implications and Management

• Early diagnosis and intervention are important to potentially reverse bronchial wall dilatation in early disease 2, 5
• Treatment should target the underlying cause when identified 2
• For ABPA, corticosteroid treatment may be beneficial 2
• For MAC infection, treatment with a macrolide, ethambutol, and a rifamycin is considered first-line therapy 2
• Airway clearance techniques offer a modest benefit in increasing sputum volume 1
• Selected patients with localized bronchiectasis causing intolerable symptoms despite maximal medical therapy should be considered for surgical treatment 1
• Exacerbations should be treated with appropriate antibiotics based on likely causative pathogens 1