WHAT YOU SHOULD KNOW ABOUT USHER SYNDROME
Christiane Tourtet B.A.
April 01, 2008
Usher syndrome is a condition that is inherited and causes progressive vision loss due to retinitis pigmentosa (RP), as well as severe hearing loss that usually occur at birth or shortly thereafter. RP is a group of diseases that are inherited and cause peripheral (side) loss of vision through the degeneration of the retina, progressively. The retina is the tissue which is light-sensitive, located at the back of the eye, and is crucial for vision.
Three types of Usher syndrome have been described by researchers:
TYPE I: Persons with this type of syndrome experience problems with balance at an early age, and are completely or nearly deaf. In early adolescence they usually begin
to exhibit signs of RP.
TYPE II: Individuals with this type of syndrome, have normal balance, but later in adolescence, experience symptoms of RP, and have moderate to severe hearing impairment.
Type III: People who have this type of syndrome have normal hearing at birth, but develop RP and then, hearing loss, progressively.
The types of the Usher syndrome are inherited as an autosomal recessive trait, which means, that a person having the syndrome receives an abnormal gene from each of her or his parents. However, if a person inherits a gene from only one parent, that person will be a carrier, but will not develop the disease.
An individual with Usher syndrome has to pass on, one disease gene to each of her or his children, but unless the person has children with another carrier of Usher genes, the children of this person are not at risk for developing the disease. As of now, it is not possible to reasonably test everyone for carrier status, but there is a possibility that this may change in the years ahead.
Testing of vision and hearing can be done to diagnose Usher syndrome. The testing includes:
1- Function tests for vision such as visual fields and electroretinogram (ERG)
2- Examination of the retina
3- Tests for hearing
4- Tests for all patients that are ten years and older to check their balance.
Even though, some of the genes that cause Usher syndrome have been identified, the diagnosis is, at present time still based on clinical and ocular testing. The genetic testing for the syndrome is done only as part of projects for research, due to many factors, such as, Usher syndrome is not caused by only one gene. As a matter of fact 10 Usher genes have been mapped : 7 for type I, 3 for type II, and 1 for type 3. Some of these genes have been sequenced and described., such as MYO7A, harmonin, CDH23, PCDH15, all of them causing type I. Type II is caused by the usherin gene. There are still many more genes to find, and this is very important for the fight against Usher syndrome. Much more study is necessary to be able to characterize these genes, and to find out, how the mutated genes cause Usher syndrome, as well as identifying additional genes that cause Usher syndrome. Throughout the world many researchers are working hard on Usher syndrome, and findings from this research may very well be, some day, the turning point for the development of treatments for Usher syndrome.
At the National Eye Institute, researchers have been following persons with Usher syndrome (Research Protocol # 93-EI-0161), and are available for examination and consultation with patients. The hearing and vision of each person is evaluated as well as samples of blood taken and studied to better understand the genes involvement in Usher Syndrome.
Resource:
National Eye Institute, U.S. National Institutes of Health.
© 2008 Christiane Tourtet, all rights reserved.
Three types of Usher syndrome have been described by researchers:
TYPE I: Persons with this type of syndrome experience problems with balance at an early age, and are completely or nearly deaf. In early adolescence they usually begin
to exhibit signs of RP.
TYPE II: Individuals with this type of syndrome, have normal balance, but later in adolescence, experience symptoms of RP, and have moderate to severe hearing impairment.
Type III: People who have this type of syndrome have normal hearing at birth, but develop RP and then, hearing loss, progressively.
The types of the Usher syndrome are inherited as an autosomal recessive trait, which means, that a person having the syndrome receives an abnormal gene from each of her or his parents. However, if a person inherits a gene from only one parent, that person will be a carrier, but will not develop the disease.
An individual with Usher syndrome has to pass on, one disease gene to each of her or his children, but unless the person has children with another carrier of Usher genes, the children of this person are not at risk for developing the disease. As of now, it is not possible to reasonably test everyone for carrier status, but there is a possibility that this may change in the years ahead.
Testing of vision and hearing can be done to diagnose Usher syndrome. The testing includes:
1- Function tests for vision such as visual fields and electroretinogram (ERG)
2- Examination of the retina
3- Tests for hearing
4- Tests for all patients that are ten years and older to check their balance.
Even though, some of the genes that cause Usher syndrome have been identified, the diagnosis is, at present time still based on clinical and ocular testing. The genetic testing for the syndrome is done only as part of projects for research, due to many factors, such as, Usher syndrome is not caused by only one gene. As a matter of fact 10 Usher genes have been mapped : 7 for type I, 3 for type II, and 1 for type 3. Some of these genes have been sequenced and described., such as MYO7A, harmonin, CDH23, PCDH15, all of them causing type I. Type II is caused by the usherin gene. There are still many more genes to find, and this is very important for the fight against Usher syndrome. Much more study is necessary to be able to characterize these genes, and to find out, how the mutated genes cause Usher syndrome, as well as identifying additional genes that cause Usher syndrome. Throughout the world many researchers are working hard on Usher syndrome, and findings from this research may very well be, some day, the turning point for the development of treatments for Usher syndrome.
At the National Eye Institute, researchers have been following persons with Usher syndrome (Research Protocol # 93-EI-0161), and are available for examination and consultation with patients. The hearing and vision of each person is evaluated as well as samples of blood taken and studied to better understand the genes involvement in Usher Syndrome.
Resource:
National Eye Institute, U.S. National Institutes of Health.
© 2008 Christiane Tourtet, all rights reserved.
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