Aug. 27, 2008 -- If you've got a certain gene mutation, you may be less likely to develop the dry form of age-related macular degeneration, new research shows.
Age-related macular degeneration (AMD), the leading cause of vision loss in the U.S., typically strikes after age 55. It affects the macula, a spot at the back of the retina that's needed for reading, driving, watching TV, and other tasks that involve central vision.
AMD comes in two forms: dry and wet. In dry AMD, the more common form, tiny yellow deposits form beneath the macula. In wet AMD, abnormal blood vessels grow and leak around the retina.
Researchers in China and the U.S. report that a certain variation of the TLR3 gene seems to protect against advanced dry AMD, but not wet AMD. They learned that by comparing genes in hundreds of people with and without AMD; their findings appear in The New England Journal of Medicine's online early edition.
The scientists, who included Zhenglin Yang, MD, of the Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital in Chengdu, China, also did lab tests on cells from human eyes and in mice. Those tests showed that the TLR3 gene variant likely guards against dry AMD by suppressing the death of certain cells in the retina.
Yang's team also speculates that people with the TLR3 gene variant may not be good candidates for experimental drugs that seek to treat wet AMD by silencing certain genes, including the protective gene variant.
"You might cure the individual of one thing and increase their risk in something else," researcher Nicholas Katsanis, PhD, of Johns Hopkins University, states in a news release. That is, those experimental drugs may treat wet AMD but raise the risk of dry AMD by turning off the protective gene variant in certain people.
That doesn't mean that those experimental drugs wouldn't help other people who don't have the protective gene variant. One day, a gene test might help predict "what kind of therapeutic paradigm might be most appropriate" for each patient, notes Katsanis.