Can you provide a concise summary of airway aspergillosis?

Airway Aspergillosis: Clinical Summary

Airway aspergillosis encompasses a spectrum of Aspergillus infections affecting the tracheobronchial tree and lung parenchyma, ranging from allergic reactions to life-threatening invasive disease, with clinical presentation determined primarily by the patient's immune status and presence of underlying lung disease. 1, 2

Clinical Forms Based on Immune Status

Chronic Pulmonary Aspergillosis (CPA) - Non-Immunocompromised Patients

Chronic cavitary pulmonary aspergillosis (CCPA) is the most common form, occurring in patients with pre-existing structural lung disease (tuberculosis, COPD, bronchiectasis) who develop one or more pulmonary cavities with significant symptoms and radiological progression over at least 3 months. 3, 1

Key diagnostic features include:

• Duration criterion of ≥3 months is critical - symptoms present for less than 3 months suggest more aggressive invasive disease requiring different management 1
• Aspergillus IgG/precipitins positive in >90% of cases 1, 4
• CT shows cavities with irregular walls, possible fungal balls (aspergillomas), and progressive expansion 3, 4
• Respiratory cultures positive in 56-81% of cases 3

Simple aspergilloma represents a single fungal ball in a pre-existing cavity with minimal symptoms and no progression over 3 months, requiring only serological or microbiological evidence of Aspergillus. 3, 1

Chronic fibrosing pulmonary aspergillosis (CFPA) is the severe end-stage form with fibrotic destruction of at least two lung lobes and major loss of lung function. 1

Subacute Invasive Aspergillosis (SAIA) - Mildly Immunocompromised

SAIA occurs over 1-3 months in moderately immunocompromised patients (chronic corticosteroid use, diabetes, cirrhosis, malnutrition) with more rapid progression than CPA. 3, 1

Distinguishing features:

• Both Aspergillus antibody AND antigen detectable in serum 3, 1
• Histology shows hyphae invading lung parenchyma 3, 1
• Variable CT findings including cavitation, nodules, and progressive consolidation 1
• Positive galactomannan in blood or respiratory fluids 1

Invasive Pulmonary Aspergillosis - Severely Immunocompromised

Invasive aspergillosis presents as necrotizing pneumonia or tracheobronchitis in severely immunocompromised patients (neutropenia, hematopoietic stem cell transplant, high-dose corticosteroids). 1, 5

Clinical presentation:

• Primary symptoms: fever, cough, dyspnea, chest pain, hemoptysis, hypoxemia 1
• CT shows "halo sign" (ground-glass surrounding nodule) early, "air crescent sign" with cavitation as disease progresses 1
• Aspergillus serology typically negative in invasive disease (unlike CPA) 1

Allergic Bronchopulmonary Aspergillosis (ABPA)

ABPA affects asthmatic patients or those with cystic fibrosis through immunologic hypersensitivity reactions to Aspergillus antigens colonizing the airways. 6, 2

Key features:

• Prevalence up to 13% in asthma clinics 6
• Presents as poorly controlled asthma with recurrent pulmonary infiltrates and bronchiectasis 6
• A. fumigatus-specific IgE is the most sensitive diagnostic test 6

Critical Diagnostic Approach

For any cavitary lung lesion present ≥3 months, evaluate for CPA with Aspergillus IgG/precipitins testing. 4

The differential diagnosis algorithm:

• Mycobacterial infection is the primary differential - TB or NTM may precede, follow, or occur simultaneously with CPA 3, 7
• Send pulmonary samples for AFB smear, mycobacterial culture, fungal culture, and galactomannan 4
• Geographic fungi (histoplasmosis, coccidioidomycosis, paracoccidioidomycosis) distinguished by antibody/antigen testing and cultures 3, 7
• Thick-walled irregular cavities in smokers suggest malignancy requiring tissue diagnosis 7

Management Principles

Voriconazole is first-line therapy for CCPA with loading dose 6 mg/kg IV q12h × 2 doses, then 4 mg/kg IV q12h or 200 mg PO q12h. 4

Alternative for CCPA: itraconazole with long-term therapy required 3

Simple aspergilloma is best managed with surgical resection when feasible. 3

SAIA and invasive disease require aggressive antifungal therapy with voriconazole or other mold-active agents based on established invasive aspergillosis protocols. 3

Common Pitfalls

• Finding Aspergillus in sputum is not diagnostic alone - the fungus is ubiquitous and can represent colonization, but presence in bronchoscopic specimens is far more consistent with infection 3
• Dual infections are common - diagnosing mycobacterial infection does not exclude CPA, and patients may have worse outcomes with concurrent infections 3, 4
• Pulmonary infiltrate volume may increase during the first week of effective antifungal therapy - this does not indicate treatment failure 4
• Necrotic lung carcinoma can mimic aspergilloma radiographically - tissue diagnosis required for definitive differentiation 7
• Persistent lung cavities may be superinfected with conventional bacteria (S. pneumoniae, H. influenzae, S. aureus, P. aeruginosa) requiring concurrent antibacterial treatment 3