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Allergic Bronchopulmonary Aspergillosis (ABPA)

Definition

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Etiology & Epidemiology

• Causative organism: Aspergillus fumigatus (almost all cases); rarely other Aspergillus spp. or fungi
• Occurs in ~2.5% of asthmatic patients referred to secondary care
• More common in patients from the Indian subcontinent
• In cystic fibrosis: up to 15% of teenagers are affected
• (Harrison's, p. 6271)

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Pathophysiology

• Aspergillus spores are inhaled and germinate in bronchi
• In atopic individuals → Type I hypersensitivity (IgE-mediated) + Type III hypersensitivity (IgG immune complex-mediated)
• Results in:
  • Eosinophilic inflammation
  • Bronchial wall damage
  • Mucous plug formation
  • Progressive bronchiectasis (central, proximal)

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Clinical Features

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Stages of ABPA (Rosenberg-Patterson Staging)

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Diagnostic Criteria (ISHAM 2013 / Rosenberg Criteria)

Obligatory criteria (both must be present):

1. Asthma or cystic fibrosis
2. Positive Aspergillus skin-prick test OR elevated serum Aspergillus-specific IgE

Other criteria (≥2 required):

• Total serum IgE > 1000 IU/mL
• Elevated serum Aspergillus-specific IgG (precipitins)
• Chest X-ray/CT infiltrates consistent with ABPA
• Central/proximal bronchiectasis on HRCT
• Peripheral blood eosinophilia (>500 cells/μL)

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Investigations

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Treatment

1. Systemic Glucocorticoids (First-line)

(Harrison's, p. 7966)

2. Antifungal Agents (Steroid-sparing / Adjunctive)

• Reduce antigenic stimulus → modulate disease activity
• Used when steroids are not tolerated or disease is recurrent
• Monitor liver function during azole therapy

3. Biologics (Severe/Refractory ABPA)

4. Supportive

• Inhaled corticosteroids + bronchodilators for underlying asthma
• Chest physiotherapy / mucus clearance techniques
• Avoid environmental Aspergillus exposure

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Complications

• Central bronchiectasis (pathognomonic)
• Pulmonary fibrosis (Stage V)
• Chronic respiratory failure
• Aspergilloma formation
• Steroid-related side effects (osteoporosis, DM, hypertension)

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Prognosis

• Early diagnosis and treatment can prevent progression to fibrosis
• Regular monitoring of serum IgE is the best marker of disease activity and relapse
• Relapses (Stage III) are common; each episode treated like Stage I

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Key Points to Remember (Exam Highlights)

• Organism: Aspergillus fumigatus | Mechanism: Type I + III hypersensitivity
• Hallmark lab: Total IgE >1000 IU/mL
• Hallmark imaging: Central bronchiectasis + high-attenuation mucus (HAM) on HRCT
• First-line: Prednisolone 0.5 mg/kg/day tapered over 3–6 months
• Antifungal: Itraconazole 200 mg BD × 4–6 months
• Stage V = end-stage fibrosis (irreversible)

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ABPA — Latest Guidelines (Full Details)

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1. DIAGNOSTIC FRAMEWORK — ISHAM Working Group Criteria (Current Standard)

Predisposing Conditions (Must have at least one):

• Bronchial asthma
• Cystic fibrosis (CF)

Obligatory Criteria (Both required):

Other Criteria (≥2 of the following):

Note (2021 update): Some working groups now accept total IgE >500 IU/mL as a lower threshold in patients already on corticosteroids, since steroids suppress IgE levels.

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2. ABPA SUBTYPES (ISHAM Classification)

HAM is considered a marker of severe/difficult-to-treat ABPA and predicts steroid dependence.

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3. STAGING — Revised Patterson Staging

Stages IV and V are not reversible — prevention by early treatment is key.

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4. INVESTIGATIONS (Workup Protocol)

Serological:

Skin Testing:

• Immediate skin-prick test to A. fumigatus extract — wheal ≥3 mm at 15 min = positive
• Intradermal test if skin-prick is equivocal

Imaging:

• Fleeting/migratory infiltrates
• "Gloved finger" sign — dilated bronchi filled with mucus
• Tramline shadows, ring shadows
• Toothpaste / Y-shaped opacities (mucoid impaction)
• Upper lobe collapse/consolidation

Sputum:

• Fungal hyphae on microscopy
• Eosinophils
• Charcot-Leyden crystals
• Culture: A. fumigatus (not diagnostic alone)

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5. TREATMENT — Latest Guidelines

PHASE 1: ACUTE STAGE (Stage I / III)

A. Oral Corticosteroids (First-line — universally recommended)

• Monitor: Total serum IgE every 6–8 weeks
• Target: ≥35% reduction in IgE = remission
• Rising IgE (>2× baseline) = exacerbation → restart full-dose steroids

Low-dose protocol (Indian guidelines / Aggarwal 2016):

• Prednisolone 0.5 mg/kg/day × 1–2 weeks → alternate day × 6–8 weeks → slow taper
• Comparable efficacy with fewer side effects

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B. Antifungal Therapy (Steroid-sparing / Adjunctive — current standard of care)

• Exacerbating/recurrent ABPA
• Steroid-dependent ABPA (Stage IV)
• Patients who cannot tolerate corticosteroids
• ABPA complicating cystic fibrosis
• As steroid-sparing agents in all acute episodes (some guidelines recommend routine use)

• LFTs at baseline and every 4–6 weeks
• Drug-drug interactions (CYP3A4)
• Itraconazole drug levels (therapeutic drug monitoring recommended)

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PHASE 2: MAINTENANCE / REMISSION

• Inhaled corticosteroids (ICS) — high dose (e.g., budesonide 800 mcg/day or fluticasone 500 mcg BD) for underlying asthma control
• Long-acting bronchodilators (LABA) as per asthma step-up therapy
• Regular IgE monitoring every 3–6 months
• Annual HRCT if clinically indicated

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PHASE 3: REFRACTORY / SEVERE ABPA — Biologics

A. Omalizumab (Anti-IgE monoclonal antibody)

B. Mepolizumab (Anti-IL-5)

C. Benralizumab (Anti-IL-5Rα)

D. Dupilumab (Anti-IL-4Rα / IL-13)

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6. TREATMENT IN SPECIAL POPULATIONS

ABPA in Cystic Fibrosis (CF-ABPA):

• Diagnosis is harder — baseline IgE is elevated, and bronchiectasis is pre-existing
• Threshold: IgE >500 IU/mL with 2× rise; use CF-specific ISHAM criteria
• Steroids: Same prednisolone regimen; caution with growth suppression in children
• Itraconazole: First-line antifungal; use oral solution for better absorption
• Omalizumab: Preferred biologic in CF-ABPA
• Avoid: Aminoglycosides and azole combinations without monitoring (renal/hepatic toxicity)

ABPA in Pregnancy:

• Prednisolone is safe (lowest effective dose)
• Itraconazole is teratogenic — CONTRAINDICATED in first trimester; avoid throughout if possible
• Use amphotericin B if antifungal absolutely needed in pregnancy

Pediatric ABPA:

• Prednisolone: 1–2 mg/kg/day (max 40–60 mg) × 2 weeks → taper
• Itraconazole: 5 mg/kg/day (max 200 mg/day)
• Monitor growth on long-term steroids

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7. MONITORING PROTOCOL (Follow-up)

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8. RESPONSE CRITERIA

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9. KEY POINTS SUMMARY TABLE

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ISHAM 2024 ABPA Guidelines — Current Status

What was revised in the 2021 ISHAM guidelines (most current full version):

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Regarding "ISHAM 2024":

• No new standalone ISHAM 2024 ABPA guideline document has been widely published or indexed in major medical databases (PubMed, MEDLINE) as a full revision.
• Some 2023–2024 updates exist as consensus statements and position papers from individual authors (Agarwal R, Denning DW), published in journals such as Mycoses, CHEST, and Clinical Infectious Diseases, refining specific areas.

Key 2023–2024 Published Updates (evidence-based):

1. Diagnostic Updates

• Dupilumab effect on IgE: Dupilumab paradoxically raises total IgE early in treatment — 2024 expert consensus recommends not using total IgE alone for diagnosis in patients on dupilumab; use Aspergillus-specific IgE + HRCT instead.
• Seronegative ABPA: Recognized as a distinct entity — patients with classic CT findings (HAM, central bronchiectasis) but IgE <1000 IU/mL; diagnosis now requires MDT discussion.
• Molecular diagnostics: Aspergillus-specific IgE component testing (rAsp f1, f2, f3, f4, f6) being validated for improved specificity — rAsp f4 and rAsp f6 most specific for ABPA vs. simple sensitization.

2. Treatment Updates (2023–2024 consensus)

• Low-dose prednisolone regimen now preferred over high-dose in most patients:
  • Prednisolone 0.25–0.5 mg/kg/day × 2 weeks → taper over 3–4 months
  • High-dose regimen (0.5–1 mg/kg/day) only for severe/HAM-positive ABPA
• Goal: Minimize cumulative steroid dose (prevent adrenal suppression, osteoporosis, DM)

• Itraconazole 200 mg BD × 4–6 months — remains standard
• Therapeutic drug monitoring (TDM) now strongly recommended: trough itraconazole >0.5 mg/L (ideally 1–4 mg/L)
• Voriconazole 200 mg BD — second line (more adverse effects: photosensitivity, neurotoxicity)
• Posaconazole — for azole-resistant or azole-intolerant cases
• 2024 expert consensus: Combination of steroids + itraconazole recommended as initial therapy for all Stage I and III patients (not just refractory), particularly those with HAM or recurrent exacerbations

3. Monitoring Updates

• Total IgE monitoring remains gold standard for relapse detection
• In patients on biologics that suppress eosinophils/IgE, use CT findings + clinical symptoms as primary monitoring tools
• HRCT should be repeated at 6 months after initial treatment to assess for new bronchiectasis or HAM resolution

4. ABPA in Cystic Fibrosis (CF) — 2024 Position

• CFTR modulators (Elexacaftor/Tezacaftor/Ivacaftor — ETI/Trikafta) have significantly reduced ABPA prevalence in CF patients in recent studies (2022–2024)
• Mechanism: Improved mucociliary clearance → less fungal colonization
• Monitoring: CF patients on CFTR modulators still require annual Aspergillus-IgE and IgE screening

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Summary: What Is New vs. 2013

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Important note: If you need the exact ISHAM 2024 full document, it should be accessed directly via:

• European Respiratory Journal or Mycoses journal (Agarwal R et al.)
• ISHAM website: www.isham.org
• PubMed search: "ABPA guidelines 2024 Agarwal"

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ALLERGIC BRONCHOPULMONARY ASPERGILLOSIS (ABPA)

Complete Reference — Harrison's 21st Ed + ISHAM 2024 Guidelines

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1. DEFINITION

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2. EPIDEMIOLOGY

• HLA associations: HLA-DR2, HLA-DR5 increase susceptibility; HLA-DQ2 is protective
• Genetic polymorphisms: IL-4Rα, IL-13, SP-A, CFTR mutations increase risk

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3. PATHOPHYSIOLOGY

A. fumigatus spores inhaled
        ↓
Germination in bronchi (defective mucociliary clearance)
        ↓
Th2-skewed immune response
        ↓
IgE (Type I) → mast cell degranulation → bronchoconstriction
IgG/IgM (Type III) → immune complexes → eosinophilic inflammation
        ↓
Bronchial wall damage → mucoid impaction → central bronchiectasis
        ↓
(If untreated) → fibrosis → respiratory failure

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4. CLINICAL FEATURES

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5. DIAGNOSTIC CRITERIA — ISHAM 2024 (OFFICIAL)

STEP 1 — Predisposing Conditions (suspect ABPA in):

• Bronchial asthma
• Cystic fibrosis
• Bronchiectasis
• COPD with compatible clinicoradiological features (mucus plugging, finger-in-glove opacities, transient infiltrates)

STEP 2 — Essential Criteria (BOTH required):

Key change from 2013: IgE threshold lowered to 500 IU/mL for higher sensitivity. Use ≥1000 IU/mL as a stronger supporting value.

STEP 3 — Additional Criteria (≥2 of the following):

Special rule (2024): Presence of High-Attenuation Mucus (HAM) on HRCT alone confirms ABPA diagnosis even if not all other criteria are fulfilled — HAM is pathognomonic.

STEP 4 — Screening Recommendation (NEW in 2024):

• Recommend screening for A. fumigatus sensitization using specific IgE in all newly diagnosed asthmatic adults at tertiary care
• Suggest screening only in difficult-to-treat asthmatic children (not all children)

Allergic Bronchopulmonary Mycosis (ABPM):

• ABPA-like presentation with normal A. fumigatus-IgE
• Requires repeated sputum culture of causative non-Aspergillus fungus (e.g., Candida, Helminthosporium, Curvularia)
• Treat identically to ABPA

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6. INVESTIGATIONS

Serology:

Skin Testing:

• Immediate skin-prick test to A. fumigatus extract
• Wheal ≥3 mm at 15 min = Type I hypersensitivity

Spirometry:

• Obstructive pattern (FEV₁/FVC reduced)
• Monitor FEV₁ every 3–6 months

Sputum:

• Fungal hyphae, eosinophils
• Charcot-Leyden crystals (breakdown of eosinophil granules)
• Culture: A. fumigatus (guides diagnosis but not sufficient alone)
• ISHAM 2024 recommends fungal sputum culture routinely

Bronchoscopy:

• Diagnosis uncertain or sputum nondiagnostic
• Unexplained haemoptysis
• Possible concomitant infection (TB) before starting steroids

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7. IMAGING

Chest X-Ray Findings:

HRCT Chest (Gold Standard):

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8. RADIOLOGICAL CLASSIFICATION — ISHAM 2024 (NEW)

Categories 3 and 4 indicate higher disease activity and poorer outcomes. Category 5 is irreversible.

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9. CLINICAL STAGING — ISHAM 2024 REVISED (5 States)

Treatment Response Criteria (NEW — Objective Multidimensional, ISHAM 2024):

• Major improvement in symptoms (Likert scale or VAS ≥50%)
• Improvement in chest radiograph/CT
• Reduction in serum total IgE ≥20% from baseline

This replaces the older "35% IgE fall" rule with a lower, more clinically realistic threshold.

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10. TREATMENT — ISHAM 2024 GUIDELINES (FULL DETAILS WITH DOSAGES)

KEY PRINCIPLE: Do NOT treat asymptomatic ABPA (ISHAM 2024 recommendation)

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A. ACUTE ABPA (Newly Diagnosed — State 1 / Exacerbation — State 3)

OPTION 1: Oral Corticosteroids (Monotherapy — RECOMMENDED)

Maximum daily dose: Usually capped at 40–60 mg/day based on body weight.

OPTION 2: Itraconazole Monotherapy (RECOMMENDED as alternative to steroids)

• Take with food or cola (acidic environment improves absorption)
• Therapeutic drug monitoring (TDM): strongly recommended — trough level 0.5–4 mg/L
• Monitor LFTs at baseline, 4 weeks, then every 6–8 weeks
• Avoid: antacids, PPIs, H2 blockers (reduce absorption)

2024 update: Itraconazole monotherapy is now formally recommended as an equivalent first-line alternative to prednisolone for acute ABPA — not just adjunctive.

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OPTION 3: Prednisolone + Itraconazole Combination

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B. ANTIFUNGAL OPTIONS (Full Details)

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C. MAINTENANCE (Remission — State 2)

• Inhaled corticosteroids (ICS): High-dose (budesonide 800 mcg/day or fluticasone 500 mcg BD) for asthma control
• LABA as per step-up asthma therapy (GINA guidelines)
• Oral steroids: Wean completely if possible
• No routine antifungal in remission unless treatment-dependent

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D. TREATMENT-DEPENDENT ABPA (State 4)

• Prolonged steroid taper (lowest effective dose)
• Itraconazole long-term (6–12+ months with TDM)
• Consider biologics as steroid-sparing agents (see below)

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E. BIOLOGICS — ISHAM 2024 + 2024 Meta-Analysis Evidence

Monitoring on biologics: Use CT findings + clinical symptoms as primary endpoints (not IgE alone) when on dupilumab or omalizumab, since these agents directly alter IgE levels.

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11. SPECIAL POPULATIONS

ABPA in Cystic Fibrosis (CF-ABPA):

• Diagnosis harder — baseline IgE elevated, bronchiectasis pre-existing
• Use CF-specific ISHAM criteria: IgE ≥500 IU/mL + ≥2× rise from baseline
• CFTR modulators (Trikafta/ETI): 2022–2024 data show significant reduction in ABPA prevalence in CF — improved mucociliary clearance reduces fungal colonization
• Omalizumab = preferred biologic in CF-ABPA
• Annual screening: A. fumigatus-IgE + total IgE even in patients on CFTR modulators

ABPA in Pregnancy:

• Prednisolone: safe — use lowest effective dose
• Itraconazole: teratogenic — CONTRAINDICATED (especially first trimester)
• If antifungal absolutely required: consider inhaled amphotericin B (minimal systemic absorption)

Pediatric ABPA:

• Prednisolone: 1–2 mg/kg/day (max 40–60 mg) × 2–4 weeks → taper
• Itraconazole: 5 mg/kg/day (max 200 mg/day) as oral solution
• Screening: Only in difficult-to-treat asthmatic children (not routine)
• Monitor growth and bone density on long-term steroids

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12. MONITORING PROTOCOL

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13. TREATMENT RESPONSE (ISHAM 2024 — OBJECTIVE CRITERIA)

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14. DIFFERENTIAL DIAGNOSIS

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15. COMPLICATIONS

• Central bronchiectasis (pathognomonic)
• Mucoid impaction → lobar collapse
• Pulmonary fibrosis (Stage 5 / CPF — irreversible)
• Chronic respiratory failure
• Aspergilloma formation in bronchiectatic cavities
• Steroid side effects: DM, osteoporosis, hypertension, adrenal suppression, cataracts

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16. PROGNOSIS

• Early treatment prevents progression to fibrosis
• Serum IgE remains the best relapse marker
• CPF (Category 5 CT / State 5) = poor prognosis; progressive functional decline
• CFTR modulator therapy in CF patients has improved ABPA outcomes significantly (2022–2024)
• Biologics offer significant improvement in steroid-dependent disease

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QUICK EXAM SUMMARY TABLE

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• Agarwal R et al. Revised ISHAM-ABPA working group clinical practice guidelines. Eur Respir J 2024; 63(4): 2400061. PMID: 38423624
• Chen X et al. Efficacy of Biologics in ABPA: Systematic Review and Meta-Analysis. Lung 2024. PMID: 38898129
• Harrison's Principles of Internal Medicine, 21st Edition (pp. 6271, 7966)
• StatPearls / NCBI Bookshelf (2024 update reflecting ISHAM 2024)