Retinitis Pigmentosa - Risk Factors
Recent research findings suggest that in some forms of Retinitis Pigmentosa, prolonged, unprotected exposure to sunlight may accelerate vision loss. Therefore, The Foundation recommends that patients wear sunglasses and visors when outdoors.
Some women feel that their vision loss progressed more rapidly during pregnancy. However, the effect of pregnancy on Retinitis Pigmentosa has not been clinically studied.
Retinitis Pigmentosa is an inherited, genetic disease. It is caused by mutations in genes that are active in retinal cells. Gene mutations are programmed into your cells at the time of conception. Retinitis Pigmentosa is not caused by injury, infection or exposure to any toxic substance.
There are three common inheritance patterns: autosomal dominant, autosomal recessive, and X-linked.
In autosomal dominant forms of Retinitis Pigmentosa, an affected person has one gene with a mutation causing the disease paired with one healthy, normal gene. When the affected person has children with an unaffected partner, there is a 50 percent chance that the affected parent will pass the disease-causing gene to each child. The unaffected partner will only pass normal genes. In dominant diseases, a child who does not have the disease gene will not have the disease and cannot pass the disease to his or her children.
In autosomal recessive forms of Retinitis Pigmentosa, unaffected parents, who are carriers, have one gene with a disease-causing mutation paired with one normal gene. Each of their children then has a 25 percent chance (or 1 chance in 4) of inheriting the two diseased genes (one from each parent) needed to cause the disorder. Carriers are unaffected because they have only one copy of the gene.
In X-linked forms of Retinitis Pigmentosa, the gene for the disease is located on the X chromosome. Females have two X chromosomes and can carry the disease gene on one of these X chromosomes. Because they have a healthy version of the gene on their other X chromosome, X-linked diseases typically do not affect females. Sometimes, however, when carrier females are examined, the retina shows minor signs of the disease.
Males have only one X chromosome paired with one Y chromosome and are therefore genetically susceptible to X-linked diseases. Males cannot be carriers of X-linked diseases. Males affected with an X-linked disease always pass the gene on the X chromosome to their daughters, who then become carriers. Affected males never pass an X-linked disease gene to their sons because fathers pass the Y chromosome to their sons.
Female carriers have a 50 percent chance (or 1 chance in 2) of passing the X-linked disease gene to their daughters, who become carriers, and a 50 percent chance of passing the gene to their sons, who are then affected by the disease.
It is important to remember that because Retinitis Pigmentosa is an inherited disorder, it commonly affects other members of a family. If someone in your family is diagnosed with a retinal degeneration, it is strongly advised that all members of the family contact an eye care professional.