High attenuation mucus
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) 1.
It may be present in up to 28 % of patients with allergic bronchopulmonary aspergillosis 2. It may be more common in patients with unilobar plugging.
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.
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.
Hyperattenuating mucus is considered an independent predictor of poorer outcomes in allergic bronchopulmonary aspergillosis.
History and etymology
The occurrence of high attenuation mucoid impaction in ABPA was first described by Goyal et al.
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