Although it's unclear why it's so, scientists at Johns Hopkins have linked a gene that allows for the chemical breakdown of the tough, protective casing that houses insects and worms to the severe congestion and polyp formation typical of chronic sinusitis.
A team of Hopkins sinus experts has found that the gene for the enzyme, acidic mammalian chitinase (AMCase), is up to 250 times more active in people with severe sinus inflammation that persists even after surgery when compared to patients in whom surgery is successful. Sinus surgery is usually the treatment of last resort for those who do not respond to drug therapy. But nearly one in 10 of those treated see symptoms return within weeks or months after surgery fails to keep open the nasal passages, scientists say.
The Hopkins report, published in the July issue of the American Journal of Rhinology, is believed to be the first to identify the enzyme's presence in the nose and confirm its link to sinusitis.
"This finding does not mean that there are actually parasites in the nose causing sinusitis, but our study does lend support to the concept that really severe and persistent sinusitis may be a case of a misplaced immune response directed against parasites that are not really there," says study lead author Andrew Lane, M.D., an associate professor at The Johns Hopkins University School of Medicine and director of its rhinology and sinus surgery center.
Previous research by other scientists had looked at the enzyme's tie-ins to asthma, which, like nasal polyps, is an inflammatory response of the body's immune system. The theory, Lane says, is that allergies and asthma result from genes that control the body's defenses against parasites, but these genes are dormant in healthy people. However, when turned on by so-called ghost parasites, the potent inflammatory response is medically very difficult to control.