Usher syndrome is the most common condition that affects both hearing and vision. A syndrome is a disease or disorder that has more than one feature or symptom. The major symptoms of Usher syndrome are hearing loss and an eye disorder called retinitis pigmentosa, or RP. RP causes night-blindness and a loss of peripheral vision (side vision) through the progressive degeneration of the retina. The retina is a light-sensitive tissue at the back of the eye and is crucial for vision. As RP progresses, the field of vision narrows - a condition known as "tunnel vision" - until only central vision (the ability to see straight ahead) remains. Many people with Usher syndrome also have severe balance problems.
There are three clinical types of Usher syndrome: Type 1: born with a profound hearing loss, retinitis pigmentosa, andbalance problems
Individuals with Type I Usher Syndrome have a profound hearing lossin all frequencies and are considered to be deaf from birth
Type 2: born with a moderate to severe hearing loss, retinitis pigmentosa,and no balance problems.
Individuals with Type II Usher Syndrome have a moderate hearing lossin the lower frequencies. In the higher frequencies it is severe or profound.The loss does not get worse as the person ages. These persons are consideredto be hard-of-hearing and usually find hearing aids to be useful
Type 3:hearing loss that gets worse over time, retinitis pigmentosa,and may have balance problems.
Individuals with Type III Usher Syndrome have a progressive hearingloss which gets significantly worse as the person ages. Most of the documentedType III cases are in Finland
Photograph of the retina of a patient with Usher syndrome (left) compared to a normal retina (right). The optic nerve (arrow) looks very pale, the vessels (stars) are very thin and there is characteristic pigment, called bone spicules (double arrows).
What causes Usher syndrome?Usher syndrome is inherited, which means that it is passed from parents to their children through genes. Genes are located in almost every cell of the body. Genes contain instructions that tell cells what to do. Every person inherits two copies of each gene, one from each parent. Sometimes genes are altered, or mutated. Mutated genes may cause cells to act differently than expected.
Usher syndrome is inherited as an autosomal recessive trait. The term autosomal means that the mutated gene is not located on either of the chromosomes that determine a person's sex; in other words, both males and females can have the disorder and can pass it along to a child. The word recessive means that, to have Usher syndrome, a person must receive a mutated form of the Usher syndrome gene from each parent. If a child has a mutation in one Usher syndrome gene but the other gene is normal, he or she is predicted to have normal vision and hearing. People with a mutation in a gene that can cause an autosomal recessive disorder are called carriers, because they "carry" the gene with a mutation, but show no symptoms of the disorder. If both parents are carriers of a mutated gene for Usher syndrome, they will have a one-in-four chance of having a child with Usher syndrome with each birth.
Usually, parents who have normal hearing and vision do not know if they are carriers of an Usher syndrome gene mutation. Currently, it is not possible to determine whether a person who does not have a family history of Usher syndrome is a carrier. Scientists at the National Institute on Deafness and Other Communication Disorders are hoping to change this, however, as they learn more about the genes responsible for Usher syndrome
What's the treatment?There's no cure for Usher syndrome, but the earlier it's diagnosed, the more can be done to help children lead as normal a life as possible.
Hearing aids and other communication technology, cochlear implants and specialised support at school may all help the child adjust to their disabilities.
Counselling may be helpful, particularly regarding future careers. Genetic counselling is important for the individual's future plans for a family and for the rest of the family, too.
Gene therapy looks increasingly promising as a treatment for retinitis pigmentosa, but it's still many years away
Sources :
http://www.medicinenet.com/usher_syndrome/page5.htm[/url
http://www.deafblind.com/whatushe.html[/url][/url][/url]
http://www.bbc.co.uk/health/conditions/ushers1.shtml[/url][/url]
