The Etiology of Chronic Rhinosinusitis Remains Unclear

Understanding the mechanisms behind eosinophilic inflammation will allow researchers to develop pharmaceutical interventions, said Dr. Ponikau. Researchers are identifying the antigens and the receptors on the eosinophilic cells and in the process are finding ways to block this abnormal immune response to the fungi, he explained.

Dr. Bernstein does not discount the non-allergic fungal CRS theory, but we have yet to see the last word on it yet, he said. Fungi are found in the noses of people without disease, so CRS may be a sign of an immune deviation in the patient, he explained.

Most otolaryngologists have found that fungi account for a small number of CNS cases, he added. In the southwestern part of the United States, where fungus growth is high, it may be responsible for 20% to 30% of disease, he said.

Researchers have put forth a hypothesis that fungus is the cause of most CRS, but I don’t think that’s realistic, said Dr. Palmer.

Biofilms

Large colonies of bacteria called biofilms may also play a role in CRS, according to Hassan Ramadan, MD, MSc, FACS, Professor and Vicechair of the Department of Otolaryngology Head and Neck at West Virginia University. He and his colleagues conducted a prospective study of the presence of biofilms in 30 patients undergoing endoscopic sinus surgery for CRS compared with four controls without the disease.

They found an 80% correlation between CRS and microscopic evidence of biofilms, said Dr. Ramadan. All controls had healthy-appearing cilia and goblet cells without biofilms. That only 80% of CRS subjects showed evidence of biofilms in their samples may be because of the collection technique of small samples not being representative of the entire sinonasal cavity, according to the study authors. It may also be that not all CRS patients have biofilms as the underlying etiology, they wrote. Bacteria may send out messages to other bacteria to form biofilms-large lattice-like colonies-in the sinuses, said Dr. Bernstein.

Biofilms have been discovered in many chronic infectious processes, including otitis media, periodontal disease, and sinusitis, said Dr. Wang. In addition, patients with CRS and polyps have been found to have biofilms. They are difficult to eradicate with systemic antibiotics, which may explain why some CRS patients don’t respond well to the medications, she said.

I do not question that biofilm is present, but I have not seen a single piece of evidence that the biofilm is actually causing the inflammation, said Dr. Ponikau. Many people do not understand that bacterial infection produces a neutrophilic inflammation, not an eosinophilic one. In addition, no one has been able to cause an eosinophilic inflammation with a bacterial infection.