Usher Syndrome: A Genetic Disorder that Effects Vision, Hearing and Balance

Usher syndrome is an inherited condition in which a child is born deaf or with hearing loss, and progressively loses their vision due to a group of hereditary diseases of the retina, known as Retinitis Pigmentosa, or RP. With RP, the retina degenerates slowly and loses its ability to send pictures to the brain. For Usher Syndrome to be present, both conditions must be present and they must be caused by a single gene. Usher syndrome effects approximately 3 to 6 percent of all deaf children and it is believed to affect an equal number of children who are hard of hearing. Usher syndrome, itself, is more than one genetic condition. It is estimated that 1 in 10,000 adults have Usher syndrome of one type or another, and approximately 4 out of every 100,000 babies born have Usher syndrome.

Usher syndrome is an inherited disease. This means that it is passed from parent to child. In order for a child to be born with Usher syndrome, both parents must be carriers of the gene. If only one parent is a carrier, the child will not have the disease, however; if both parents carry the gene, there is a 25% chance that the child will have the disease, a 50% chance that the child will be a carrier of the disease, and a 25% chance that the child will neither have the disease nor be a carrier.

There are three types of Usher syndrome. Types 1 and 2 are most common in the United States. It is estimated that 90 to 95 percent of all cases of Usher syndrome in the United States are either type 1 or type 2.

Those who are affected with type 1 Usher syndrome are deaf at birth and have severe problems with balance. These children experience little to no benefit from the use of hearing aids. Night blindness is present in infancy or early childhood. By late childhood or early teens, blind spots in the person's vision begin to appear. By early adulthood, the person is legally blind. Children with type 1 Usher syndrome are generally slow to sit without support and rarely walk independently before the age of 18 months.

Those who are affected with type 2 Usher syndrome are born with moderate to severe hearing loss and normal balance. Night blindness begins in late childhood or early teenage years. By late teenage or early adulthood years, blind spots begin to appear in the person's vision. The person becomes legally blind in early to mid adulthood years. Children affected with type 2 Usher syndrome generally benefit from the use of hearing aids and have the ability to communicate orally. Vision problems progress more slowly than in type 1 Usher syndrome and the onset of Retinitis Pigmentosa is often not apparent until teenage years.

Those affected with type 3 Usher syndrome are born with normal hearing at birth. They progressively lose their hearing in their childhood or early teenage years. Hearing loss, once it begins, tends to progress rapidly, over a 10 to 15 year period, until hearing loss is profound. Balance problems vary in severity, but often progresses with age. The rate at which hearing and vision are lost varies from person to person, even within families where more than one person is affected. Night blindness normally begins during puberty. By the late teen to early adulthood age, blind spots begin to appear in the person's vision. By mid-adulthood years, the person may become legally blind.

Usher syndrome effects hearing, vision and balance. Because of this, diagnosis of the disorder includes testing of all three. Visual field tests to determine the person's peripheral vision, an ERG, or electroretinogram is performed to measure the electrical responses of the light-sensitive cells within the eye, and an examination of the retina and other parts in the back of the eye to determine any abnormalities are all tests done to determine vision and vision loss. A hearing test is performed to determine how loud sounds need to be in a specific frequency before the person hears them. This helps to monitor and determine any hearing loss. To test the person's balance, an ENG, or electronystagmogram is performed to measure any involuntary eye movements.

There is currently no cure for Usher syndrome. Early detection is best for helping those affected learn how to cope with this disorder. There are many educational programs available to help. Typical treatment will include hearing aids, cochlear implants, assisted listening devices and/or other communication methods, including the teaching of sign language. Other services are available to help teach the affected person how to communicate with others to the best of their ability, retain mobility, live as independently as possible, read by using Braille, as well as other low-vision services and auditory training.

Some ophthalmologists believe that a high dose of Vitamin A palmitate may slow the progression of vision loss due to Retinitis Pigmentosa. Because of this, some ophthalmologists will recommend a daily supplement of Vitamin A palmitate at the dosage of 15,000 IU daily. Those who use this form of treatment should be careful not to exceed the daily dose. It is important to note that this treatment is not recommended for those with type 1 Usher syndrome. Some guidelines are in place for those who use this type of treatment. These guidelines include not substituting Vitamin A palmitate with a beta-carotene supplement, not taking more than the recommended dosage, women who are using this treatment should stop treatment three months before trying to conceive a child due to the increased risk of birth defects, and women who are pregnant should stop this treatment due to the risk of birth defects. In addition to these guidelines, a person using this treatment should not consume more than 400 IU of Vitamin E each day.

Usher disease, although not fatal, can be very debilitating for those who are affected. Early diagnosis along with education and training can help those individuals live a more productive and independent life. The sooner the disorder is diagnosed, the sooner treatment can begin. If you suspect that your child may be affected by Usher syndrome, the best thing you can do is seek a medical opinion.

Sources for this article include:
http://www.medicinenet.com/script/main/art.asp?articlekey=16228&pf=3&page=1
http://www.dbproject.mm.org/ushersyndrome.html
http://www.deafblind.com/usher.html