Thursday, March 09, 2006

AMD Causes 19

Chapter Two
What Causes AMD?

Researchers and doctors don’t yet know exactly what causes AMD, but we’re getting closer. AMD is most strongly associated with age and a family history of the disease. Why does age increase the risk? The answer to that may simply be that most diseases increase as we age. It takes time for genetic or environmental factors to cause damage. It takes time for the wonderful cells in our body to wear out. A person doesn’t get lung cancer after smoking one cigarette or heart disease after eating one cheeseburger. A person may have some abnormal genes and then be exposed to environmental factors that increase his or her chances of developing the condition, but it may still take seventy years for the disease to show up.
Genes and Inflammation

There is good evidence that there is a large genetic component to AMD. Studies have shown that the risk of AMD is much higher for people whose family members have the disease than for people who have no family history of AMD. Identical twins, who share the same genes, often have similar features of age-related macular degeneration. Abnormalities in the fibulin 5 and 6 genes, which code for structural proteins that are found in and around the outer parts of the retina and choroid, have recently been shown to be associated with AMD in some families.

Researchers are working very hard to find more genes associated with AMD. Finding the genes is difficult, though, because macular degeneration is probably not a single disease and the changes we see in the retina, namely the drusen, atrophy, and neovascularization, can probably be caused by the interaction of a lot of different genes with many different environmental factors.

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