5 July 2005
Three new studies published in Science Express have implicated a single gene in the disease age-related macular degeneration (AMD), with one report suggesting that the presence of the genetic defect may account for up to 50% of the risk of an individual developing AMD [Alberts et al. (2005) Science: 1110189]. The macula is a small area in the centre of the retina, the part of the eye that focuses incoming light to form images and relays this information to the brain. There are two main forms of age-related macular degeneration; around 10% of cases are wet (exudative) AMD, where tissue degeneration causes a fluid build-up under the retina; this form of the disease can sometimes be treated with laser therapy. However, the majority of cases are dry (atrophic or non-exudative) AMD, a slow deterioration in the function of the visual cells for which there is currently no treatment. Both forms of the disease affect central vision. Overall, AMD represents the leading cause of blindness among the over sixties and currently affects around half a million people in the UK, with this figure likely to rise as the population ages.
Researchers screened individuals with AMD and family members, as well as unrelated individuals without AMD. They found that those people with one or more copies of a particular variant of the CFH (complement factor H) gene were more likely to have AMD than those who lacked the genetic variant. The CFH mutation was reportedly present in half of all those tested who had AMD, and showed a particularly strong association with wet AMD. The risk of developing AMD for individuals homozygous for the CFH mutation was found to be several times greater than for people without the variant. Dr Margaret Pericak-Vance, Director of the Duke Center for Human Genetics in the US and a co-author of one Science paper, commented: "The finding may ultimately lead to new methods for identifying those at high risk for macular degeneration and suggests new pathways for drug development", adding that in the shorter-term, it could aid the identification of individuals at high risk of developing AMD and allow preventative lifestyle changes to decrease that risk, such as avoiding smoking and obesity (see BBC news report).