Can Aspergillus cause bronchiectasis?

Aspergillus as a Cause of Bronchiectasis

Yes, Aspergillus can cause bronchiectasis, primarily through allergic bronchopulmonary aspergillosis (ABPA), which is a well-established cause of bronchiectasis. 1

Mechanisms by which Aspergillus causes bronchiectasis

Allergic Bronchopulmonary Aspergillosis (ABPA)

ABPA is the most common Aspergillus-related condition that leads to bronchiectasis. It occurs through an immune-mediated inflammatory response to Aspergillus fumigatus antigens in susceptible individuals, typically those with asthma or cystic fibrosis. 1

The pathophysiology involves:

• Hypersensitivity reaction to inhaled Aspergillus spores
• Immune-mediated inflammation causing bronchial wall damage
• Progressive airway destruction leading to permanent dilation of bronchi (bronchiectasis)

Diagnostic criteria for ABPA

According to the revised ISHAM-ABPA working group guidelines (2024), the diagnosis of ABPA requires: 1

• Clinical deterioration (increased cough, wheeze, increased sputum production, worsening lung function)
• Total serum IgE level >500 IU/mL
• Immediate cutaneous reaction to Aspergillus (skin prick test weal >3 mm)
• Increased Aspergillus-specific IgE antibodies

Other Aspergillus-related conditions that can lead to bronchiectasis

1. Aspergillus bronchitis: Chronic infection with Aspergillus in the airways can lead to inflammation and eventual bronchiectasis, particularly in patients with pre-existing structural lung disease. 2, 3

2. Chronic pulmonary aspergillosis: Long-term Aspergillus infection can cause progressive lung damage including bronchiectasis, especially in patients with underlying lung conditions. 4

3. Aspergillus sensitization: Recent evidence from the European Bronchiectasis Registry shows that patients with bronchiectasis who have Aspergillus sensitization (elevated Aspergillus-specific IgE without meeting full ABPA criteria) experience more severe disease with worse lung function and more frequent exacerbations. 5

Clinical implications and management

Recognition of Aspergillus in bronchiectasis

• Approximately 6.1% of patients with bronchiectasis have ABPA 5
• An additional 5.7% show Aspergillus sensitization 5
• 8.1% have raised Aspergillus-specific IgG without sensitization 5

Diagnostic approach

1. Test for Aspergillus in patients with bronchiectasis, especially those with:

   • History of asthma
   • Recurrent exacerbations
   • Central bronchiectasis on imaging
   • Mucus plugging

2. Recommended tests include:

   • Total serum IgE
   • Aspergillus-specific IgE
   • Aspergillus-specific IgG
   • Blood eosinophil count
   • Aspergillus skin prick test

Treatment considerations

• Corticosteroids are the mainstay of treatment for ABPA-related bronchiectasis
• Antifungal therapy may be indicated in some cases
• Do not routinely use antifungal therapy without evidence of fungal disease, as fungal cultures can be positive in patients receiving long-term antibiotic therapy 1

Pitfalls and caveats

1. Diagnostic challenges: Aspergillus can be a colonizer rather than a pathogen in bronchiectasis patients. Positive sputum cultures alone do not confirm pathogenicity. 6

2. Multiple etiologies: Patients with ABPA may also have additional underlying causes of bronchiectasis, so a comprehensive evaluation for other etiologies (immunodeficiencies, ciliary disorders, mycobacterial infection) is recommended. 1

3. Overlapping conditions: The distinction between Aspergillus colonization, sensitization, and ABPA can be challenging, as these conditions exist on a spectrum and may evolve from one to another. 3

4. Treatment monitoring: Regular monitoring of total IgE levels is important to assess response to therapy in ABPA-related bronchiectasis.

In conclusion, Aspergillus plays a significant role in the pathogenesis of bronchiectasis, primarily through ABPA but also through other mechanisms. Recognition of Aspergillus-associated conditions in bronchiectasis patients is crucial for appropriate management and prevention of disease progression.