Overview
Definition:
Allergic Bronchopulmonary Aspergillosis (ABPA) is a hypersensitivity reaction to the fungus Aspergillus fumigatus, occurring in the airways of susceptible individuals, particularly those with underlying conditions like Cystic Fibrosis (CF)
It is characterized by central bronchiectasis and mucus plugging, leading to progressive lung damage.
Epidemiology:
ABPA occurs in approximately 10-15% of pediatric patients with Cystic Fibrosis
Incidence increases with age, and it is a significant cause of lung function decline and morbidity in this population
The prevalence can vary based on geographical location and Aspergillus sensitization rates.
Clinical Significance:
ABPA represents a treatable exacerbating factor in CF lung disease
Early diagnosis and prompt management are crucial to prevent irreversible airway damage, including bronchiectasis and fibrosis, which can lead to severe respiratory insufficiency and reduced quality of life
Recognizing ABPA is vital for optimal CF care.
Clinical Presentation
Symptoms:
New or worsening cough, often productive of thick, brownish mucus plugs
Wheezing and dyspnea
Fever with chills
Chest pain or tightness
Hemoptysis, though less common
Recurrent or persistent pulmonary infiltrates on imaging.
Signs:
Crackles (rales) on lung auscultation, especially in upper lobes
Diffuse wheezing
Possible signs of malnutrition or dehydration in severe CF patients
Clubbing of digits in advanced disease
Peripheral eosinophilia (absolute eosinophil count > 500 cells/µL).
Diagnostic Criteria:
Diagnostic criteria for ABPA in CF typically include the presence of characteristic clinical features, immunological evidence of sensitization to Aspergillus fumigatus, and characteristic radiological findings
Commonly used criteria require: 1
Clinical evidence of CF
2
Peripheral eosinophilia (>500 cells/µL)
3
Elevated total IgE (>417 IU/mL)
4
Precipitating antibodies to Aspergillus fumigatus (IgG or IgA)
5
Immediate (Type I) skin reactivity to Aspergillus fumigatus antigen
6
Radiographic evidence of central bronchiectasis, transient infiltrates, or mucus plugging
Not all criteria are always met, and a composite approach is often used.
Diagnostic Approach
History Taking:
Detailed history of CF diagnosis and management
Previous episodes of wheezing, cough, or infiltrates
Sputum characteristics (color, consistency)
History of asthma or atopy
Recent exposure to Aspergillus-rich environments
Family history of allergic diseases.
Physical Examination:
Systematic examination of the respiratory system, focusing on lung auscultation for crackles and wheezing
Assess for signs of respiratory distress
Evaluate for peripheral eosinophilia
General assessment for nutritional status and hydration.
Investigations:
Complete Blood Count (CBC) with differential to assess eosinophilia
Serum total IgE levels to screen for elevated levels
Aspergillus fumigatus specific IgE and IgG antibodies to confirm sensitization and immune response
Serum precipitins to Aspergillus fumigatus
Chest X-ray or CT scan to identify central bronchiectasis, mucoid impaction, and infiltrates
Sputum microscopy and culture for Aspergillus (may be positive but not diagnostic for ABPA).
Differential Diagnosis:
Other causes of pulmonary infiltrates in CF, such as bacterial pneumonia or atypical infections
Allergic bronchopulmonary mycotoxicosis
Eosinophilic pneumonia
Bronchiolitis
Allergic fungal sinusitis
Allergic asthma without CF.
Management
Initial Management:
The primary goal is to suppress the allergic inflammatory response and reduce mucus plugging
Initial management involves corticosteroids and often an antifungal agent.
Medical Management:
Oral corticosteroids (e.g., Prednisolone) are the mainstay of treatment, typically initiated at 0.5-1 mg/kg/day and tapered slowly over several weeks to months, guided by clinical and serological response
Antifungal agents like Itraconazole or Voriconazole are often used in conjunction with corticosteroids to reduce Aspergillus burden and enhance treatment efficacy
Bronchodilators may be used for symptomatic relief of bronchoconstriction
Mucolytics can help with mucus clearance.
Surgical Management:
Surgical intervention is generally not indicated for ABPA
It is primarily managed medically
In rare, refractory cases with localized, irreversible bronchiectasis causing significant morbidity, surgical resection of the affected lobe might be considered as a last resort, but this is exceptionally uncommon and carries high risks.
Supportive Care:
Aggressive airway clearance techniques are essential for CF patients with ABPA to remove mucus plugs and improve lung function
Nutritional support should be optimized
Regular monitoring of IgE levels, eosinophil counts, and pulmonary function tests is crucial to assess treatment response and guide long-term management
Prompt treatment of any superimposed bacterial infections is also vital.
Complications
Early Complications:
Acute exacerbations of ABPA, leading to worsening respiratory symptoms and increased need for corticosteroids
Superadded bacterial infections
Bronchospasm.
Late Complications:
Progressive central bronchiectasis, leading to irreversible lung damage
Pulmonary fibrosis
Respiratory failure
Hemoptysis
Aspergilloma formation in pre-existing cavities
Increased risk of colonization with other pathogens.
Prevention Strategies:
While primary prevention of sensitization to Aspergillus is difficult, early recognition and prompt treatment of ABPA are key to preventing long-term complications
Strict adherence to CF care guidelines, including regular monitoring for ABPA, is paramount
Minimizing exposure to known Aspergillus sources, especially in high-risk individuals, may be considered.
Prognosis
Factors Affecting Prognosis:
Early diagnosis and aggressive treatment improve prognosis significantly
Factors predicting poorer outcomes include delayed diagnosis, frequent relapses, extensive bronchiectasis at diagnosis, and severe underlying CF lung disease.
Outcomes:
With appropriate management, many patients can achieve remission of ABPA, leading to improved symptoms and stable lung function
However, ABPA can be a relapsing condition, requiring long-term monitoring and intermittent treatment
Some degree of irreversible lung damage may persist.
Follow Up:
Long-term follow-up is essential for patients with CF and ABPA
This includes regular clinical assessments, monitoring of total IgE and Aspergillus-specific IgE levels, chest imaging as needed, and ongoing optimization of CF management
The goal is to detect and manage relapses early and prevent disease progression.
Key Points
Exam Focus:
ABPA is a hypersensitivity reaction to Aspergillus in CF
Key diagnostic markers include eosinophilia, elevated IgE, Aspergillus-specific antibodies, and central bronchiectasis
Corticosteroids are the primary treatment, often combined with antifungals
Monitor IgE and eosinophils to assess response and relapses.
Clinical Pearls:
Always consider ABPA in a CF patient with new or worsening respiratory symptoms, especially if there is eosinophilia or transient infiltrates
Differentiate from simple exacerbations or bacterial infections
Slow tapering of steroids is crucial to prevent rebound flares
Antifungals can synergize with steroids and reduce steroid burden.
Common Mistakes:
Delaying diagnosis due to overlooking Aspergillus as a trigger
Inadequate duration or dosage of corticosteroid therapy
Abrupt discontinuation of steroids
Failing to monitor serological markers for treatment response or relapse
Misinterpreting transient infiltrates as solely bacterial pneumonia without considering ABPA.