<prompt> The most common cause of fungal sinusitis is REPEAT QUESTIONA fumigatesA nigerA flavusCandida  <response>: Fungal infections of the paranasal sinuses are uncommon and usually occur in individuals who are immunocompromised. Aspergillus fumigatus is most commonly involved in allergic fungal sinusitis and sinus mycetoma. Ref: Textbook of diseases of ENT, PL DHINGRA, 7th edition, pg no. 220 