Fungal cultures of the nasal mucus are dubious in the diagnosis of any form of fungal sinusitis. Hyphae penetrate the sinus mucosa into submucosa, blood vessels, or bone in invasive disease. To distinguish between these two forms, ample quantities of sinus contents and biopsy specimens of diseased and healthy mucosa and bone bordering the area of frank necrosis must be obtained for histopathological analysis. Allergic fungal sinusitis should be suspected in patients with atopy, chronic often intractable sinusitis and nasal polyposis. AFS has a slow mild course and there is no tissue invasion, expansion or erosion of the sinus wall.
Sinuses contain brown or greenish black material.
Leyden crystals, cellular debris, and sparse hyphae rarely visualised without fungal stains. Sinus mucosa has a mixed cellular infiltrate of eosinophils, plasma cells, and lymphocytes. Coronal CT scan showing right fungal sinusitis. The most common causes of allergic fungal sinusitis are the dematiaceous moulds including curvularia lunata, pseudallescheria boydii, bipolaris species, and the hyaline moulds such as aspergillus species and fusarium species. These fungi are also common causes of allergic rhinitis.