Synopsis
Recognise allergic bronchopulmonary aspergillosis as a treatable airway hypersensitivity syndrome, apply contemporary diagnostic criteria, distinguish activity from background structural lung disease, and monitor treatment without relying on a single laboratory value.
- ABPA is an exaggerated immune response to airway colonisation by Aspergillus, most often in asthma or cystic fibrosis; it is distinct from simple sensitisation and invasive aspergillosis.
- The revised ISHAM framework requires compatible disease or presentation, Aspergillus fumigatus sensitisation and raised total IgE, with additional immunological or imaging evidence rather than one positive test alone.
- Current diagnostic thresholds include A. fumigatus-specific IgE at least 0.35 kUA/L and total IgE usually at least 500 IU/mL, interpreted with steroid exposure, age and the clinical picture.
- Central bronchiectasis, mucus plugging and transient pulmonary opacities support ABPA; high-attenuation mucus on CT is especially persuasive and can establish the diagnosis despite an otherwise incomplete criterion set.
- A sputum culture growing Aspergillus neither proves allergic disease nor predicts activity, while a negative culture does not exclude the immunological syndrome.
- Total IgE is useful as an individual trend: establish a post-treatment baseline and investigate a substantial rise alongside symptoms and imaging rather than trying to normalise it completely.
- Acute symptomatic ABPA is commonly treated with a planned systemic corticosteroid course or an oral azole; recurrent disease may justify combination or steroid-sparing treatment under a specialist.
- Azole treatment needs formulation-specific counselling, interaction screening, liver monitoring and usually therapeutic drug monitoring; prescribing it casually can cause toxicity or ineffective exposure.
Key red flags
Expectoration of tenacious brownish plugs, segmental collapse or finger-in-glove impaction suggests obstructing allergic mucin. Extensive plugging with hypoxaemia requires urgent airway and imaging assessment.
Fever, pleuritic pain, cavitation, haemoptysis, neutropenia or major immunosuppression broadens the differential to bacterial pneumonia, chronic pulmonary aspergillosis or invasive fungal infection and should accelerate specialist review.
Investigation priorities
Demonstrate fungal sensitisation as an essential diagnostic component.
Management branches
Uncontrolled asthma, unexplained mucus plugging or deterioration in cystic fibrosis or bronchiectasis raises suspicion of ABPA.
- Request A. fumigatus-specific IgE and total IgE, then add eosinophils, fungus-specific IgG and thin-section CT when sensitisation and clinical features make ABPA plausible.
- Apply current ISHAM criteria explicitly, recording whether each essential and supportive component is met and noting recent systemic steroid exposure that could suppress results.
- Exclude bacterial infection and other aspergillus syndromes, then agree the diagnosis and baseline activity measures with respiratory, CF or bronchiectasis specialists before starting prolonged treatment.