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Allergic fungal sinusitis was previously thought to be caused solely by Aspergillus species. The list has expanded to include dematiaceous fungi, including Bipolaris, Exserohilum, Curvularia, Alternaria, and Drechslera. The histologic appearance of allergic mucin is the same irrespective of the causative organism. The causative agent in this case was Bipolaris. Isolated fungal hyphae are seen in this PAS-stained section of the thick mucus.