Fungi & Sinusitis

Current research from Mayo clinic indicates that 96% of patients suffering from sinusitis were found to have fungal growth associated with an increase in eosinophiles. The result is a release of MBP (Major Basic Protein) into the mucus which attacks and kills the fungus but is very irritating to the lining of the sinuses. It is believed that MBP injures the lining of the sinuses and allows the bacteria to proliferate "Fungus allergy was thought to be involved in less than 10% of cases", says Dr Sherris. "Our studies indicate that in fact fungus is the likely cause in nearly all of these problems as it is not an allergic reaction, but an immune reaction to fungus, of which over 40 different kinds were identified."

The Mayo Clinic suggests that fungal sinusitis may be much more common than previously thought. The disease is now known as EFRS (eosinophilic fungal rhinosinusitis) or EMRS (eosinophilic mucinous rhinosinusitis). Fungal growth was found in washings from the sinuses in 96% of patients with chronic sinusitis. Normal controls had almost as much growth, the difference being that those patients with chronic sinusitis had eosinophiles ( a type of white blood cell involved in allergic and other reactions) which had become activated. As a result of the activation, the eosinophiles released a product called MBP (Major Basic Protein) into the mucus which attacks and kills the fungus but is very irritating to the lining of the sinuses. We believe that MBP injures the lining of the sinuses and allows the bacteria to proliferate. The injury to the lining of the sinuses by the fungus and mucus led to the belief that treatment of chronic sinusitis should be directed at the fungus rather than the bacteria.

Obviously the optimal treatment would address the reason the eosinophiles attack the fungus, however, at the present time, we do not know the reason. There has been much speculation about why people develop the sensitivity to fungi. Some people believe that it is as a result of extensive use of antibiotics causing overgrowth of fungi. Others believe that it is the result of extensive exposure to mold and fungi in the environment.

As more data has accumulated, there is more evidence that the problem may be as important as the Mayo Clinic suggests and the significance is starting to be accepted. Prior to the Mayo group's work on fungal sinusitis, it was recognized that there were several types of fungal sinusitis. Whenever a new finding is discovered in medicine, it is often met with resistance. It becomes important for that finding to be confirmed by an independent group. This has now been accomplished by a well respected group from Graz, Austria.

They were able to show positive fungal cultures in 92 % of their patients. Almost as many of the controls also had fungi. Clusters of eosinophiles were found around fungi in 94 % of patients. This is important because we believe that this shows that the eosinophiles are involved in attacking and killing the fungi.

Prior to the reports from the Mayo clinic, fungal sinusitis was well known, but thought to be much less common. Patients who have repeated bouts of sinusitis, as well as those who are immunocompromised should be considered to possibly have a fungal sinusitis. Cultures are best obtained from the sinuses, as nasal cultures are unreliable. Fungal sinusitis is broken down into several categories: Allergic, Fungus balls (Mycetoma), and Invasive. Allergic fungal sinusitis (AFS) is commonly caused by Aspergillus, as well as Fusarium, Curvularia, and others. Patients often have associated asthma. The criteria include CT or MRI confirmation, a dark green or black material the consistency of peanut butter called "allergic mucin" which typically contain a few hyphae, no invasion, and no predisposing systemic disease. Charcot-Leyden crystals, which are breakdown products of eosinophiles are often found.

This disease is analogous to Allergic Bronchopulmonary Aspergillosis. This problem is most similar to the type described at the Mayo clinic, but these patients have a much different character to their mucus. Fungus balls often involve the maxillary sinus and may present similarly to other causes of sinusitis including a foul smelling breath. In addition to radiological abnormalities, thick pus or a clay-like substance is found in the sinuses. There is no allergic mucin, but dense hyphae are found. There is no invasion. There is an inflammatory response in the mucosa. Upon looking into the sinus, the fungus ball can vary in size from 1 mm or smaller to a size which completely occupies the sinus. It may have a greenish-black appearance. Removal of the fungus ball is the typical treatment. Invasive sinusitis can progress rapidly, and typically necessitates surgery, often on a emergent basis and often requiring Amphotericin B intravenously as well. There have been some forms of invasive sinusitis which can cause proptosis. There is a form of chronic invasive fungal sinusitis which is associated with visual abnormalities due to bony erosion from the ethmoids.

Mayo Clin Proc. 1999 Sep;74(9):877-84.