Three teams of researchers have identified a gene mutation that increases the risk of age-related macular degeneration (AMD), a common cause of blindness in the elderly. The discovery could help identify people who are vulnerable to the condition. Although the causes of AMD are thought to include many genetic and non-genetic factors, the scientists think that variations in the gene could account for up 50 per cent of a person's risk of developing the disorder.

AMD causes the gradual degeneration of the central part of the retina, an area known as the macula, which eventually leads to a complete loss of central vision. Three US teams, who all reported their findings in the early online edition of the journal Science, all discovered that a single gene mutation greatly increases the likelihood that a person will develop AMD. The gene makes an immune system protein called complement factor H (CFH), and the scientists think that the mutated version could lead to excessive inflammation.

Researchers based at the Duke University Medical Center in North Carolina studied 182 families affected by AMD, 495 isolated cases of the disease and 185 unaffected people. They found that around half of those with AMD - or in affected families, those who were at risk of developing it - had at least one copy of the mutated CFH gene. Team leader Margaret Pericak-Vance said: 'The finding may ultimately lead to new methods for identifying those at high risk for macular degeneration and suggest new pathways for drug development'. However, she also said that in the short-term, it might also be possible to identify those at risk of developing AMD and for them to make lifestyle changes that could cut their risk of developing the disorder. Smoking and obesity are both thought to increase the risk of AMD, for example, whereas eating leafy green vegetables can lower it.

The Duke scientists' findings were confirmed by two other groups, based at Yale University School of Medicine in Connecticut and the University of Texas Southwestern Medical Center. The discovery adds weight to the suggestion that inflammation is at the root of macular degeneration. 'The whole idea that inflammatory processes are involved in human diseases has taken on a lot of steam in recent years', said US AMD researcher Lincoln Johnson. He added that anti-inflammatory drugs, or those that target the complement system, might one day help treat or prevent AMD.