November 2000
BALTIMORE - Gene alterations known to cause cystic fibrosis (CF), which is characterized by mucous membrane abnormalities in the lungs, appear also to contribute to chronic sinus problems in some people, according to a recent study.
About 14% of the general U.S. population suffers from chronic sinusitis. The disease occurs frequently in patients with asthma and those with allergic rhinitis.
Sinusitis occurs commonly in people with CF, a disorder now diagnosed by the presence of alterations in a gene known as CFTR, according to Garry Cutting, MD, and his colleagues at the Johns Hopkins University here.
They compared the DNA of 147 patients with sinusitis to that of 123 people without sinusitis to see if the CFTR gene was present. Patients with CF were excluded from the study, which was recently published in the Journal of the American Medical Association.
CFTR's job is to regulate the flow of salt and water across the cell membrane. People with CF carry two copies of an altered CFTR gene, which affects the membranes in the lungs and leads to accumulation of thick, sticky mucous that is not only difficult to clear, but also provides a breeding ground for bacteria.
"Certainly many things contribute to chronic sinusitis in people who have no known family history of cystic fibrosis," said Cutting. "But we wondered if at least some sinusitis sufferers in the general population might also carry a variant of one copy of the CFTR gene that contributes to their sinusitis but spares them of cystic fibrosis."
Analysis of the DNA samples from the patients revealed CF mutations in the CFTR gene in 10 of the 147 volunteers who had chronic sinusitis but not CF. Each of the sinusitis sufferers had characteristic thickening of the mucous membranes in the nose and sinuses.
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Results showed that sinusitis sufferers were nearly five times more likely than healthy people to carry a CFTR alteration associated with CF. Of the 10 patients who did have CF-linked alterations, nine also carried another CFTR variant known as M470V, which occurs in about 50% of the general population.
In recent years, chronic sinusitis has accounted for more than 11 million visits to doctors' offices. Often, the condition can be controlled with decongestants, antihistamines and nasal corticosteroid sprays. Sometimes antibiotics are added to the regimen. Several of the patients in Cutting's study had also received sinus surgery multiple times. Yet, even those efforts fail to relieve the condition in some patients.
The study is among the first to investigate the genetic basis of chronic sinusitis. It was supported by National Institute of Allergy and Infectious Diseases, the National Institute of Diabetes and Digestive and Kidney Diseases, the National Center for Research Resources, all components of the National Institutes of Health (NIH), and the Cystic Fibrosis Foundation.
For more information:
- Wang XJ et al. Mutation in the gene responsible for cystic fibrosis and predisposition to chronic rhinosinusitis in the general population. JAMA. 2000:284(14):1814-19.
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