Invasive and non-invasive syndromes of fungal sinusitis have certain common features. They both may occur in immunocompetent or immunocompromised persons, may have an acute or chronic course, and may spread to the orbit, structures of the eye, and the brain. Purulent, pasty, often foul-smelling material is present within the affected sinuses. Aspergillus is the most common reported cause of fungal sinusitis. 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.