ARMD
Just two genes, Factor H and Factor B, cause blindness in millions
By IANS
Mar 6, 2006, 16:56

Just two genes cause blindness in millions of older people across the globe, a discovery that scientists say could aid the development of new treatments for the condition.

Nearly three-quarters of people in the world suffer from age-related macular degeneration (AMD) a most common cause of blindness. AMD is marked by a progressive loss of central vision due to degeneration of the macula - a region of the retina responsible for fine, central vision.

Researchers at New York's Columbia University studied 1,300 people and found that this common cause of blindness was linked to just two genes - Factor H and Factor B. While Factor H is an inhibitor of the immune response to infection, Factor B is an activator, the online edition of BBC News reported.

"I am not aware of any other complex disorder where nearly 75 percent of genetic causality has been identified," lead researcher Rando Allikmets said.

Factor H controls the production of a protein that helps shut down the body's immune response to infection once it has been successfully fought off.

People with these inherited variants of Factor H are less able to control inflammation caused by infectious triggers, which may spark AMD in later life, they said.

The researchers found 74 percent of the people with AMD had either the Factor H or Factor B risk factor or both - but no protective variants of either gene.

"These findings are significant because they absolutely confirm the roles of these two genes and, consequently, the central role of a specific immune response pathway, in the development of AMD," Allikmets said.

"In just a few short years, we've gone from knowing very little about what causes AMD to knowing quite a lot. We now have clear targets for early therapeutic intervention," Allikmets said.

The researchers are now searching for the specific triggers that set off the immune response, and subsequent inflammation.

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