Allergic Fungal Sinusitis (Allergic Fungal Rhinosinusitis)

What allergic fungal sinusitis is

Fungal spores are everywhere in the air, and most people breathe them in harmlessly. In AFRS, a person with a tendency to allergy (atopy) mounts a strong allergic reaction, involving IgE antibodies and eosinophils, to fungi that settle in the sinuses. Common culprits are dematiaceous (darkly pigmented) molds such as Bipolaris, Curvularia and Alternaria, and Aspergillus.

The reaction causes:

• swelling of the sinus lining and nasal polyps
• thick, sticky allergic mucin, full of eosinophils and fungal fragments, often described as looking like peanut butter or axle grease
• blocked sinus drainage, so more fungus and mucus collect, which feeds the cycle

Over time, the trapped mucin can slowly expand and thin the bony walls of the sinuses. It can push into the eye socket or toward the brain, but it does not invade living tissue.

How it differs from other fungal sinus disease

AFRS is the most common form of fungal sinus disease and one of the recognized subtypes of chronic sinusitis with polyps. It is also distinct from other forms of aspergillosis that affect the lungs.

Symptoms

• gradually worsening blocked nose
• thick, dark or discolored nasal mucus, sometimes coughed or blown out in firm plugs
• reduced or lost sense of smell
• facial pressure, though usually less pain than other sinusitis
• symptoms often affecting one side more than the other
• nasal polyps visible in the nostrils
• in advanced cases, a widened bridge of the nose, an eye that is pushed forward or outward, or double vision

Many people also have allergic rhinitis, and some have asthma.

Risk factors

• allergies to molds and other airborne allergens
• adolescence and young adulthood (average age in the 20s)
• living in warm, humid regions, such as the southern United States
• immune system that is normal (unlike invasive fungal disease)

Diagnosis

Doctors commonly use the Bent and Kuhn criteria, which include:

1. Type I allergy to fungi, confirmed by skin or blood tests
2. Nasal polyps
3. Characteristic CT findings
4. Eosinophilic mucin without fungal invasion of tissue
5. Fungi seen on stain or grown in culture from the mucin

Tests used:

• Nasal endoscopy: a thin camera shows polyps and thick mucin.
• CT scan of the sinuses: shows expanded, filled sinuses, often one-sided, with bright, mixed-density material and thinning of the bony walls.
• MRI: shows a typical pattern and helps assess the eye socket or skull base.
• Blood tests: total IgE (often very high) and fungal-specific IgE.
• Pathology: of material removed during surgery.

Treatment

Surgery

Functional endoscopic sinus surgery is the first step. Through the nostrils, the surgeon removes polyps and all allergic mucin and opens the sinuses widely so they drain and can be reached by rinses and sprays. Removing all fungal material reduces the allergic stimulus.

After surgery

• Oral steroids: a course after surgery reduces inflammation and recurrence.
• Steroid nasal sprays or high-volume steroid sinus rinses: long term.
• Saline irrigations: daily, to clear mucus.
• Allergy immunotherapy: sometimes used to reduce sensitivity to fungi and other allergens.
• Biologic medicines: such as dupilumab, which targets type 2 inflammation and is approved for chronic rhinosinusitis with nasal polyps. They may help recurrent AFRS.
• Antifungal medicines: have limited and mixed evidence and are not routinely recommended.

Outlook

AFRS is a chronic condition that tends to come back, with recurrence in many patients, especially if follow-up and medicines lapse. Regular ENT follow-up with endoscopy, ongoing rinses and steroid sprays, and prompt treatment of recurrence give most people good control. Revision surgery is sometimes needed.

Frequently asked questions

What is allergic fungal sinusitis?

Allergic fungal sinusitis is a form of chronic sinusitis caused by an allergic reaction to fungi trapped in the sinuses. It produces thick allergic mucus and nasal polyps that block the sinuses. It is not an invasive infection and is not contagious.

What are the symptoms of allergic fungal sinusitis?

Symptoms include a gradually worsening blocked nose, thick dark mucus, loss of smell, nasal polyps and facial pressure, often worse on one side. In advanced cases, the eye can be pushed out of position, causing double vision.

How is allergic fungal sinusitis treated?

The main treatment is endoscopic sinus surgery to remove polyps and fungal mucus and open the sinuses. This is followed by oral steroids, steroid sprays or rinses, and saline irrigations. Allergy immunotherapy and biologic medicines can help prevent recurrence.

Is allergic fungal sinusitis dangerous?

It is not usually dangerous, because the fungus does not invade tissue. However, untreated disease can expand the sinuses and press on the eye or skull base. Invasive fungal sinusitis, a different condition in people with weak immunity, is dangerous and needs emergency care.

Does allergic fungal sinusitis come back after surgery?

Yes, it often recurs, especially without ongoing treatment. Daily rinses, steroid sprays or rinses, regular endoscopic follow-up and, in some cases, immunotherapy or biologic medicines reduce the chance of recurrence.