Allergic Bronchopulmonary Aspergillosis in Children

Allergic Bronchopulmonary Aspergillosis (ABPA) is a complex hypersensitivity reaction to the fungus Aspergillus fumigatus, primarily affecting children with asthma or cystic fibrosis. It is characterized by recurrent pulmonary infiltrates, bronchiectasis, and potential progression to pulmonary fibrosis if left untreated.

Pathophysiology

ABPA results from a hypersensitivity reaction to Aspergillus antigens, involving both type I (IgE-mediated) and type III (immune complex-mediated) reactions. The process involves:

• Colonization of the airways by Aspergillus fumigatus
• Release of antigenic substances triggering an allergic response
• Production of specific IgE and IgG antibodies
• Activation of inflammatory cells, particularly eosinophils
• Airway damage and bronchiectasis due to persistent inflammation

Clinical Presentation

Children with ABPA may present with:

• Worsening asthma symptoms or increased inhaler use
• Recurrent pulmonary infiltrates
• Productive cough with brownish mucus plugs
• Wheezing and chest tightness
• Fever and malaise
• Hemoptysis (rare in children)

In children with cystic fibrosis, ABPA can lead to more frequent exacerbations and accelerated decline in lung function.

Diagnosis

Diagnosis of ABPA in children requires a combination of clinical, radiological, and immunological criteria:

1. Asthma or cystic fibrosis
2. Elevated total serum IgE (>1000 IU/mL)
3. Positive skin prick test or specific IgE to Aspergillus fumigatus
4. Elevated Aspergillus-specific IgG or precipitating antibodies
5. Pulmonary infiltrates on chest radiograph or high-resolution CT
6. Peripheral blood eosinophilia (>500 cells/μL)
7. Central bronchiectasis on CT (not always present in children)

Additional tests may include:

• Sputum culture for Aspergillus
• Pulmonary function tests showing obstructive pattern
• Serum galactomannan or (1,3)-β-D-glucan assay

Treatment

Management of ABPA in children involves:

1. Systemic corticosteroids:
   • Prednisone 0.5-1 mg/kg/day for 2 weeks, then tapered over 3-6 months
   • Aim to reduce inflammation and prevent lung damage
2. Antifungal therapy:
   • Itraconazole (5-10 mg/kg/day) or voriconazole for 3-6 months
   • Reduces fungal burden and decreases antigenic stimulation
3. Omalizumab (anti-IgE therapy):
   • Considered in refractory cases or steroid-dependent patients
   • Dosing based on weight and serum IgE levels
4. Management of underlying asthma or cystic fibrosis
5. Pulmonary rehabilitation and airway clearance techniques
6. Regular follow-up with monitoring of symptoms, lung function, and serum IgE levels

Prognosis

With proper management, the prognosis for children with ABPA is generally good. However, factors affecting prognosis include:

• Early diagnosis and treatment initiation
• Adherence to therapy
• Frequency and severity of exacerbations
• Presence and extent of bronchiectasis
• Underlying lung disease (asthma or cystic fibrosis) severity

Long-term complications may include:

• Persistent airflow obstruction
• Progressive bronchiectasis
• Pulmonary fibrosis (in severe, untreated cases)

Regular follow-up and adjustment of treatment as needed are crucial for optimizing outcomes in pediatric ABPA patients.