A 28-year-old woman with poorly controlled asthma presents with recurrent exacerbations, fever, and expectoration of brownish mucus plugs over the past 6 months. Spirometry shows FEV1/FVC ratio of 62% with FEV1 improving by 18% post-bronchodilator. Total serum IgE is 2400 IU/mL, blood eosinophils are 680 cells/µL, and Aspergillus-specific IgE is elevated. High-resolution CT chest reveals central bronchiectasis with mucoid impaction in proximal airways and high-attenuation mucus. The clinical and radiological findings marked **A** in the diagram are consistent with which diagnosis?
A. Chronic obstructive pulmonary disease (COPD) with fungal colonization
B. Allergic bronchopulmonary aspergillosis (ABPA)
C. Aspergillus fumigatus pneumonia with septic emboli
D. Idiopathic pulmonary fibrosis with bronchiectasis
Explanation
Why Allergic bronchopulmonary aspergillosis (ABPA) is right
The clinical presentation—poorly controlled asthma with recurrent exacerbations, expectoration of brownish mucus plugs, fever, and malaise—combined with the diagnostic triad of (1) elevated Aspergillus-specific IgE, (2) total serum IgE >1000 IU/mL (here 2400 IU/mL), and (3) blood eosinophilia >500 cells/µL (here 680 cells/µL) in a patient with asthma meets the ISHAM 2013 diagnostic criteria for ABPA. The spirometric pattern of reversible obstruction (FEV1 improving ≥12% and 200 mL post-bronchodilator) and the pathognomonic CT findings of central bronchiectasis (cylindrical/varicose in proximal/segmental airways with distal sparing), mucoid impaction ("finger-in-glove" sign), and high-attenuation mucus are hallmark features of ABPA, reflecting the Th2-skewed hypersensitivity response (Type I IgE-mediated and Type III immune complex) to Aspergillus fumigatus antigens chronically colonizing the airways (Agarwal et al; ISHAM 2013).
Why each distractor is wrong
Chronic obstructive pulmonary disease (COPD) with fungal colonization: COPD presents with irreversible obstruction (FEV1 does not improve significantly post-bronchodilator) and shows hyperinflation on imaging, not central bronchiectasis. The markedly elevated IgE and eosinophilia are not typical of COPD alone. Fungal colonization in COPD is secondary, not the primary pathogenic driver.
Idiopathic pulmonary fibrosis with bronchiectasis: IPF presents with a restrictive spirometric pattern (reduced FVC, normal or elevated FEV1/FVC ratio) and reduced DLCO, not an obstructive pattern with bronchodilator reversibility. IPF is characterized by interstitial fibrosis on CT, not central bronchiectasis with mucoid impaction. Eosinophilia and elevated IgE are not features of IPF.
Aspergillus fumigatus pneumonia with septic emboli: Acute aspergillus pneumonia presents acutely with fever, cough, and infiltrates but does not produce the chronic, recurrent pattern of asthma exacerbations or the diagnostic elevation of Aspergillus-specific IgE and total IgE >1000 IU/mL. Septic emboli would show wedge-shaped peripheral infiltrates, not central bronchiectasis. This condition does not involve the hypersensitivity immune response characteristic of ABPA.
High-YieldNEET PG
ABPA = asthma + reversible obstruction + central bronchiectasis + elevated IgE (>1000 IU/mL) + Aspergillus-specific IgE + eosinophilia (>500 cells/µL) — a Type I and Type III hypersensitivity response, not infection.
ISHAM Working Group on ABPA Diagnostic Criteria 2013; Agarwal et al
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