Allergic Bronchopulmonary Aspergillosis
An allergic lung reaction to Aspergillus fungus seen in asthma and cystic fibrosis patients, causing wheezing, brownish mucus plugs, and eventually permanent lung damage if not treated.
Emergency Management: Massive hemoptysis requires immediate airway protection and potential interventional radiology for embolization.
Allergic bronchopulmonary aspergillosis (ABPA) is a complex hypersensitivity reaction predominantly to Aspergillus fumigatus, occurring almost exclusively in patients with asthma or cystic fibrosis (CF). It leads to severe airway inflammation, mucous plugging, and potentially irreversible bronchiectasis and pulmonary fibrosis.
Detailed Overview
The immune system mounts an exaggerated IgE and IgG mediated response against colonizing Aspergillus species in the lower airways. This triggers intense eosinophilic inflammation. Unlike invasive aspergillosis, there is no tissue invasion by the fungus; rather, the damage is immune-mediated. Left untreated, it results in permanent architectural distortion of the lungs.
Epidemiology & Demographics
Affects 1-2% of all asthma patients (up to 13% in specialty asthma clinics) and 2-15% of patients with cystic fibrosis. Most commonly diagnosed in the 3rd to 5th decades of life.
Etiological Mechanism
Colonization of the respiratory tract by Aspergillus species, most commonly Aspergillus fumigatus, triggering a robust allergic immune response in susceptible hosts.
Primary Causes
Hypersensitivity to Aspergillus fumigatus antigens (e.g., Asp f 1, Asp f 2).
Inhaled Aspergillus conidia germinate into hyphae within the mucus of patients with underlying airway disease (asthma/CF). These secrete proteolytic enzymes and antigens. The host mounts a Th2-predominant immune response with elevated IL-4, IL-5, and IL-13, leading to massive eosinophil recruitment and high IgE production. Eosinophil degranulation causes direct airway epithelial damage, mucous hypersecretion (plugs), and ultimately bronchiectasis and fibrosis.
Diagnostic Criteria & Guidelines
Rosenberg-Patterson criteria or ISHAM criteria: 1) Predisposing condition (asthma or CF), 2) Elevated total serum IgE > 1000 IU/mL, 3) Positive Aspergillus specific IgE or skin test, 4) Elevated Aspergillus specific IgG or precipitins, 5) Central bronchiectasis on HRCT, 6) Peripheral blood eosinophilia > 500 cells/mcL.
Systemic Corticosteroids: Prednisone 0.5 mg/kg/day orally for 14 days, then taper over 3 to 6 months depending on clinical response and IgE levels. Used to suppress the intense inflammatory response. AND Antifungal therapy: Itraconazole 200 mg orally BID for 16 weeks (requires therapeutic drug monitoring for levels and LFTs) to decrease fungal burden and inflammatory stimulus.
Second-Line & Adjunctive Therapy
Biologics for refractory cases or severe corticosteroid dependence: Omalizumab (anti-IgE) dosed based on weight and IgE level, or Dupilumab (anti-IL4Ra) 300 mg SQ every 2 weeks. Alternative antifungals: Voriconazole 200 mg BID.
Surgical & Procedural Management
Surgery is rarely indicated for ABPA itself, but may be needed for life-threatening hemoptysis related to bronchiectasis (bronchial artery embolization or localized resection).
Patient Counseling & Advice
Explain that ABPA requires long-term follow-up and that adherence to medications, especially oral steroids during flares, is crucial to prevent permanent lung damage. Counsel on the side effects of prolonged steroid use (bone density loss, weight gain).
Follow-Up & Monitoring Schedule
Monitor total serum IgE every 1-2 months during acute treatment; a 35-50% reduction indicates successful response. Routine PFTs (spirometry) to monitor lung function. Annual HRCT to assess for structural progression.
Preventive Strategies
Optimal control of underlying asthma or CF. Avoidance of significant mold exposure.
Highly variable. If diagnosed and treated early (Stage I/II), structural lung damage can be prevented. Late diagnosis (Stage V) is associated with significant morbidity, chronic respiratory failure, and reduced life expectancy.