“Hyperdense Mucus Plug” Sign – CT Findings In Allergic Bronchopulmonary Aspergillosis

Abstract

Background: Allergic Bronchopulmonary Aspergillosis (ABPA) is a hypersensitivity response to Aspergillus fumigatus with varied radiological manifestations. While the differential diagnosis of central bronchiectasis is broad, identifying pathognomonic radiological features on high-resolution computed tomography (HRCT) is essential for an accurate diagnosis.

Case Presentation: A 52-year-old female with a history of asthma presented with a chronic cough and expectoration. Laboratory workup demonstrated elevated eosinophil counts and total serum IgE. Chest radiography revealed central bronchiectasis with a right upper lobe radio-opaque shadow. Unenhanced HRCT confirmed bilateral central bronchiectasis and identified hyperdense mucus plugging in the right upper lobe bronchi (density = 101 HU) distal to a large bronchocele, establishing a diagnosis of ABPA with high-attenuation mucus (ABPA-HAM). The patient was successfully treated with systemic corticosteroids and oral antifungals.

Discussion: High-attenuation mucus (HAM) is defined as mucoid impaction denser than normal paraspinal skeletal muscle. Present in up to 30% of ABPA patients, HAM correlates with increased disease severity, higher baseline serum IgE, and a greater risk of relapse following therapy.

Conclusion: The "hyperdense mucus plug" sign is a characteristic and virtually diagnostic HRCT finding in ABPA. Early recognition is critical for prompt therapeutic intervention and long-term prognostic monitoring.