On CT scan of the paranasal sinuses in a patient with left-sided chronic sinusitis, a 'halo sign' (central hyperdense material surrounded by a low-density rim) is noted in the left maxillary sinus. Which diagnosis should be considered?

• A Mucocele
• B Inverted papilloma
• C Fungal (mycetoma/saprophytic) sinusitis ✓
• D Antrochoanal polyp

Explanation

The 'halo sign' (calcified/hyperdense central material surrounded by a lower-density inflammatory rim) within the maxillary sinus on CT is characteristic of a fungal ball (mycetoma/saprophytic fungal sinusitis), caused most commonly by Aspergillus fumigatus. The central opacity represents the fungal concretions with calcium oxalate crystals. Management is surgical clearance (functional endoscopic sinus surgery with middle meatal antrostomy) — no antifungal therapy is required in immunocompetent patients.

Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.