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.
Airway persistence of Aspergillus antigens can provoke a strong type 2 inflammatory response, thick mucus, recurrent obstruction and bronchiectatic damage. ABPA should be considered when asthma becomes unexpectedly difficult to control, radiographic shadows migrate, brown plugs are expectorated, or a person with cystic fibrosis or bronchiectasis deteriorates without a sufficient bacterial explanation. Similar features may occur in other fungal-allergic airway disease, so the label should follow structured assessment.
Diagnosis is syndromic. The 2024 revised ISHAM criteria allow a predisposing condition—such as asthma, cystic fibrosis, bronchiectasis or COPD—or a compatible clinico-radiological presentation. Essential components are sensitisation to A. fumigatus and raised total IgE, followed by at least two supportive components: raised A. fumigatus-specific IgG, current or historical eosinophilia, or imaging consistent with ABPA. Results near a threshold deserve clinical interpretation, especially after systemic corticosteroids have suppressed IgE or eosinophils.
Asthma and cystic fibrosis provide mucus-rich, structurally abnormal airways in which Aspergillus can persist without necessarily invading tissue.
Repeated exposure to airborne Aspergillus antigens drives exaggerated immediate and type 2 immune responses in a sensitised host.
Atopy, impaired mucus clearance and selected immune or genetic factors increase risk, while fungal sensitisation alone remains more common than the full syndrome.
Inhaled spores germinate within retained bronchial mucus but usually remain confined to the airway lumen in immunocompetent patients.
Fungal antigens trigger IgE-mediated and eosinophilic inflammation, causing bronchospasm, airway-wall oedema and systemic immunological activity, which helps produce the characteristic physiological impairment.
Thick mucus, fungal material and inflammatory cells obstruct bronchi, producing transient opacities, segmental collapse and expectoration of plugs.
Repeated inflammation and obstruction remodel proximal bronchi, leading to central bronchiectasis, fixed airflow limitation and recurrent infection.
Repeated steroid-requiring asthma attacks, persistent wheeze, falling lung function or poor control despite credible inhaler technique should prompt sensitisation testing, especially when imaging abnormalities are recurrent or fleeting.
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.
A person with cystic fibrosis or established bronchiectasis may have ABPA superimposed on chronic sputum and infection. Look for a change in symptoms, new infiltrates and a coordinated immunological rise rather than attributing every decline to ABPA.
Transient consolidation, atelectasis or nodular branching shadows that clear and recur elsewhere are characteristic clues. Fixed advanced bronchiectasis or fibrosis may remain after immunological activity has settled.
Eosinophilia and poor control overlap, but the combination of fungal sensitisation, markedly increased total IgE and compatible imaging supports ABPA.
Positive fungal-specific allergy tests without the broader immunological and radiological syndrome indicate sensitisation rather than ABPA.
Progressive cavities, fungal balls and systemic symptoms in structurally damaged lung suggest chronic infection rather than primarily allergic airway disease.
Neuropathy, purpura, renal disease or other systemic vasculitic features distinguish eosinophilic vasculitis from lung-limited allergic disease.
Purulent sputum and bacterial growth without rising allergic markers or new mucus impaction may represent ordinary infective deterioration.
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.
Repeated mucus obstruction and inflammation permanently dilate bronchi, establishing impaired clearance and a cycle of bacterial infection.
Chronic airway remodelling can reduce reversibility and leave persistent breathlessness despite control of current allergic activity.
Large mucus plugs can occlude segmental or lobar bronchi, producing atelectasis, infection and acute worsening of gas exchange.
Repeated systemic corticosteroids cause metabolic, skeletal and infectious harm, while antifungal medicines introduce hepatic effects and interactions.
A. fumigatus-specific IgE is an essential starting point, but many sensitised people never develop ABPA; additional immune and radiological evidence prevents overdiagnosis.
High-attenuation mucus is more specific than ordinary mucus plugging and can secure the diagnosis in an otherwise compatible case that falls short on another criterion.
The useful comparator is the individual's stable value after treatment, not the laboratory upper limit; persistent elevation does not automatically mean persistent active disease.
Recent systemic corticosteroids can reduce eosinophils and total IgE, so record exposure and recover historical results before dismissing a strongly suggestive presentation.
People with damaged airways commonly develop bacterial consolidation, NTM disease or chronic aspergillus infection, each of which may worsen if reflexively treated as ABPA relapse.
Calling a positive Aspergillus sputum culture ABPA without demonstrating sensitisation and the wider diagnostic pattern.
Excluding the diagnosis because eosinophils are normal after systemic corticosteroid treatment.
Restarting prednisolone for an isolated total-IgE rise without checking symptoms, imaging and infection.
Prescribing itraconazole without reconciling interactions, formulation instructions, liver monitoring or drug-level arrangements.
Treating chronic fixed bronchiectasis as ongoing allergic activity and allowing cumulative steroid harm to grow.
Assuming ABPA is invasive aspergillosis, or overlooking invasive disease in a genuinely immunocompromised patient.
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A woman with asthma has recurrent fleeting opacities, A. fumigatus-specific IgE of 2.1 kUA/L, total IgE of 940 IU/mL, eosinophils of 0.7 × 10^9/L and CT mucus plugging. Which conclusion is best?
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.
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Confirm activity before repeating a course. Assess glucose, blood pressure, infection risk, mood, bone and gastrointestinal risks, cumulative exposure and adrenal suppression; provide steroid safety advice and prophylaxis where indicated.
Check liver function and the full medicines list for potent CYP3A and P-glycoprotein interactions. Consider negative inotropy, neuropathy and gastrointestinal effects; poor absorption or subtherapeutic levels can mimic non-response.