What is Usher Syndrome?
Usher Syndrome is the most common disease that affects the auditory system and eye. The symptoms associated with Usher Syndrome are:
The vision loss is due to Retinitis Pigmentosa or RP. Retinitis Pigmentosa affects the retinal pigment epithelial layer causing loss of vision. The vision loss is in the periphery and as it progresses the person loses their side-vision. This can continue to the point of only having a few degrees of side-vision which commonly known as tunnel vision.
There are three types of Usher Syndrome:
Types 1 and 2 are the most common in the United States comprising nearly 90 percent of cases in the United States.
What Causes Usher Syndrome?
Usher Syndrome is a autosomal recessive inherited disease. Autosomal indicates that the mutated gene is not located on the set of chromosomes that determine the sex of an individual. Therefore, men and women can have Usher Syndrome. In order to get Usher Syndrome, each parent must be a carrier of the mutated gene. If both parents are carriers of the gene for Usher Syndrome, there is a one in four chance of a child having Usher Syndrome.
Testing for Usher Syndrome
At the present time there is no test for determining if a person is a carrier. The only way to have any idea is if there is a family history of Usher Syndrome.
Incidence of Usher Syndrome
In the United States about 4 babies out of 100,000 births have Usher Syndrome. Approximately ten percent of all children who are deaf or hearing-impaired have Usher Syndrome.
Usher Syndrome Type 1
Children with Usher Syndrome type 1 are profoundly deaf at birth. These children need to be evaluated as soon as possible in order to determine the best course of action.
These children begin to have vision problems early in childhood. They usually progress rapidly to blindness.
They usually have significant balance problems and don’t begin walking until eighteen months of age.
Usher Syndrome Type 2
Children with Usher Syndrome type 2 are born with moderate to severe hearing loss.
These children have problems with their vision from Retinitis Pigmentosa later and do not usually have vision difficulties until their teenage years.
Their balance is normal.
Usher Syndrome Type 3
Children with Usher Syndrome type 3 have normal hearing at birth. Their hearing usually begins to diminish in their teens and progress into adulthood.
The vision begins to decline in their teens with night vision problems. The vision loss slowly progresses to the point of blindness in adulthood. The speed of loss can vary.
Their balance can be normal or have mild balance difficulties. They can develop balance problems later in life.
Diagnosis of Usher Syndrome
Early diagnosis is important as the child can be placed in special education programs and treatment that is available started.
A hearing test should be performed to determine the level of hearing.
A comprehensive dilated eye exam to examine the retina for signs of Retinitis Pigmentosa needs to be done. An electroretinogram (ERG) should be done to test the electrical response of the retinal cells. A visual field can be performed when the child is old enough to determine the number of degrees in their side vision.
An electronystagmogram (ENG) can be performed to measure involuntary eye movements which can show the possibility of balance problems.
Genetic Testing for Usher Syndrome
Several genetic loci of genes have been isolated and found to cause Usher Syndrome. Due to the fact that so many genes are involved in Usher Syndrome, genetic testing is not normally performed.
Treatment of Usher Syndrome
There is no specific treatment for Usher Syndrome. Treatment is targeted for the specific condition related to Usher Syndrome.
Depending on the level of hearing loss, treatment may include hearing aids, cochlear implants, and sign language.
There is no treatment for Retinitis Pigmentosa. Some eye doctors believe tht high doses of vitamin A palmitate may decrease or slow the progression of Retinitis Pigmentosa. The recommended dose is 15,000 IU of vitamin A in the palmitate form with monitoring by a physician. Braille instruction and low vision training may be beneficial.
Usher Syndrome is a autosomal recessive inherited disease involving the eye and auditory system. There is no specific treatment for Usher Syndrome. Research is being done to locate all the genes involved with possible gene therapy in the distant future. Early diagnosis is important. You can get more information at www.nidcd.nih.gov .