Causes

Fungi involved in sinusitis include:

• Aspergillus is the most common cause of all forms of fungal sinusitis.
• Other fungi include Curvularia, Bipolaris, Alternaria, Dreschslera, Cryptococcus, Candida, Sporothrix,Exserohilum, and Mucormycosis.
• There have been a few reports of fungal sinusitis caused by Metarrhizium anisopliae, which is used in biological insect control.

There are four categories of fungal sinusitis:

• Acute or invasive fungal sinusitis - This infection is most likely to affect people with diabetes and compromised immune systems.
• Chronic or indolent fungal sinusitis - This form is generally found outside the US, most commonly in the Sudan and northern India.
• Fungus ball (mycetoma) - This fungal sinusitis is noninvasive and occurs usually in one sinus, most often the maxillary sinus.
• Allergic fungal sinusitis - This form typically occurs because of an allergy to the fungus Aspergillus (rather than being caused by the fungus itself). In such cases, a peanut butter-like fungal growth occurs in the sinus cavities that may cause nasal passage obstruction and the erosion of the bones.

Fungal infections can be very serious, and both chronic and acute fungal sinusitis require immediate treatment. Fungal ball is not invasive and is nearly always treatable.

Fungal infections should be suspected in people with sinusitis who also have diabetes, leukemia, AIDS, or other conditions that impair the immune system. Fungal infections can also occur in patients with healthy immune systems but they are far less common.