Allergic fungal sinusitis (AFS) is the most common form of fungal sinusitis and is common in warm, humid climates.

The majority sinuses show near complete opacification. On unenhanced CT the sinuses are typically opacified by centrally (often serpentinous) hyperdense material with a peripheral rim of hypodense mucosa. 

Approximately 40% of patients may have each of the following features:

• expansion of an involved sinus
• remodeling and thinning of the bony sinus walls
• erosion of the sinus wall.