High attenuation mucus

Pulmonary

eosinophilia may indicate onset stage of allergic bronchopulmonary aspergillosis. Representative CT images of the EP and non-EP groups. a EP group, Case 1: pre-treatment HRCT shows infiltrates with the appearance of ground-glass opacities (small arrows) and dense consolidation (large arrow) predominantly in the peripheral upper lobes. b EP-group, Case 2: HRCT scan shows infiltrates with the appearance of ground-glass opacities (small arrows) and consolidation (large arrow) with bronchial wall thickening (small arrowheads), predominantly in the peripheral upper lobes. Non-EP group, Case 3 (c mediastinal window; d lung window): HRCT scans show patchy ground-glass opacities (small arrow) and slight HAM impaction (white arrow in c) with bronchiectasis (arrowheads) and lymph node swelling

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High-attenuation mucus (HAM) is a form of mucoid impaction which is often considered a characterisitic and an "almost pathognomonic" feature of allergic bronchopulmonary aspergillosis (ABPA) (close to 100% specificity) .

Epidemiology

It may be present in up to 28 % of patients with allergic bronchopulmonary aspergillosis . It may be more common in patients with unilobar plugging.

Pathology

Its exact basis is not clear but many consider hyperattenuating mucus attributed to the presence of calcium salts and metals (the ions of iron and manganese) or desiccated mucus.

Radiographic assessment

CT

It can be either subjectively taken as as mucus visually denser than the chest wall or paraspinal skeletal muscle or objectively defined on a CT scan as having an attenuation value > 70 Hounsfield units.