What are the CT findings and treatment for Allergic Bronchopulmonary Aspergillosis (ABPA)?

CT Findings and Treatment for Allergic Bronchopulmonary Aspergillosis (ABPA)

The CT findings in ABPA include bronchiectasis, mucus plugging, high-attenuation mucus, centrilobular nodules, and in advanced cases, fibrotic changes; treatment consists primarily of oral glucocorticoids (prednisolone 0.5 mg/kg/day for 2-4 weeks then tapered over 4 months) with antifungal agents like itraconazole as adjunctive therapy. 1

CT Findings in ABPA

ABPA is classified radiologically into five categories based on CT findings 1:

1. ABPA-S (Serological ABPA):

   • Normal chest CT findings
   • No bronchiectasis

2. ABPA-B (ABPA with Bronchiectasis):

   • Radiological evidence of bronchiectasis
   • Predominantly central (proximal) bronchiectasis, though peripheral bronchiectasis is also common 2
   • Can be cylindrical, varicose, or cystic in nature

3. ABPA-MP (ABPA with Mucus Plugging):

   • Mucus plugging without high-attenuation
   • May coexist with bronchiectasis

4. ABPA-HAM (ABPA with High-Attenuation Mucus):

   • Pathognomonic finding of high-attenuation mucus (mucus visually denser than paraspinal muscles on non-contrast CT)
   • 100% specificity but only 35% sensitivity 1

5. ABPA-CPF (ABPA with Chronic Pleuropulmonary Fibrosis):

   • Two or more of: pulmonary fibrosis, fibro-cavitary lesions, fungal ball, pleural thickening
   • Represents advanced disease

Additional Common CT Findings:

• Centrilobular nodules with tree-in-bud appearance
• Atelectasis
• Mosaic attenuation
• Consolidation (uncommon primary finding) 2

Treatment of ABPA

First-Line Treatment:

1. Oral Glucocorticoids 1, 3:

   • Dosing regimen: Prednisolone 0.5 mg/kg/day for 2-4 weeks, then tapered over 4 months
   • Primary treatment for acute ABPA
   • Goals: symptom relief, improving asthma control, preventing exacerbations, halting bronchiectasis progression

2. Antifungal Therapy 1, 3:

   • Itraconazole: 200 mg twice daily for 4 months
   • Can be used as monotherapy in patients who cannot tolerate glucocorticoids
   • Often used as adjunctive therapy with glucocorticoids
   • Target trough levels: ≥0.5 mg/L

Treatment Based on Disease Classification:

• Asymptomatic ABPA: Systemic therapy not routinely required
• Symptomatic ABPA-S or ABPA-B: Oral glucocorticoids or itraconazole monotherapy
• ABPA-MP or ABPA-HAM: Consider combination therapy (glucocorticoids plus itraconazole)
• ABPA-CPF: Aggressive therapy with combination treatment; rule out chronic pulmonary aspergillosis 1, 3

For Recurrent Exacerbations:

• Combination therapy with oral prednisolone and itraconazole
• Consider long-term itraconazole (200 mg daily) for treatment-dependent ABPA 3
• Biological agents for steroid-dependent patients:
  • Omalizumab (anti-IgE)
  • Mepolizumab (anti-IL-5)
  • Benralizumab (anti-IL-5 receptor)

Bronchiectasis Management:

• Airway clearance techniques
• Nebulized hypertonic saline (3-7%, 4-5 mL) to reduce sputum viscosity
• Consider long-term azithromycin for frequent infective exacerbations 3

Monitoring and Follow-up

• Assess response after 8-12 weeks using:
  • Clinical symptoms
  • Serum total IgE (target: ≥20% reduction)
  • Chest radiographs (not CT) for routine follow-up
• Monitor for drug interactions:
  • Between azoles and statins
  • QTc prolongation with azithromycin and itraconazole combination
• Watch for hepatotoxicity with antifungal therapy 3

Important Considerations

• High-resolution CT (1.25-1.5 mm) is essential for initial diagnosis and classification 1
• Central bronchiectasis was traditionally considered characteristic of ABPA, but peripheral bronchiectasis is now recognized as common (33-43% of cases) 2
• Chest radiographs are normal in up to 50% of cases, making CT crucial for diagnosis 2
• High-attenuation mucus (HAM) is pathognomonic but present in only about 20% of patients 4
• ABPA-CPF may progress to chronic pulmonary aspergillosis, requiring different management approaches 5