What is Usher syndrome?
Usher syndrome is the name given to a group of inherited disorders that cause hearing and vision loss. The degree of hearing impairment varies greatly. A degenerative disease of the retina called retinitis pigmentosa causes the vision loss associated with this disorder.
Usher syndrome accounts for approximately three percent of the congenitally deaf (deaf at birth) and over 50 percent of the deaf-blind community.
Type 1
Individuals with Usher syndrome type I are often born profoundly deaf or severely hearing impaired. Consequently, there may be speech abnormalities. Special testing will show abnormalities with their balance (vestibular) system, although this may not be particularly noticeable to either the patient or a doctor performing an examination. Researchers believe these symptoms are caused by a malfunctioning of the nerve cells in the cochlea in the inner ear. The symptoms of retinitis pigmentosa often begin in childhood or adolescence.Type 2
Individuals with Usher syndrome type 2 are born having mild to moderate hearing impairment. The symptoms of retinitis pigmentosa often are evident by late adolescence. The degree of hearing loss usually remains stable, and there are no problems with the vestibular (balance) system.Type 3
Individuals with Usher syndrome type 3 experience progressive hearing loss as well as vision loss caused by retinitis pigmentosa.
Hearing impairment caused by Usher syndrome is considered to be sensori-neural. Normally, nerve cells in the inner ear transport impulses to the brain to be interpreted as sounds. However, if an individual has Usher syndrome, these nerve cells are not working properly. Currently, there is no way to restore normal hearing.
The hearing loss in Usher syndrome is due to an inner ear problem which cannot be corrected with middle ear surgery. If the individual has partial hearing, a hearing aid is commonly used and can be very helpful. If an individual has a profound or complete hearing loss and is unable to hear any sound, a hearing aid may not be useful. However, in this case, cochlear implant surgery may play a role. This device receives, processes and transmits sound, bypassing the damaged parts of the inner ear.
The term retinitis pigmentosa (RP) refers to a group of inherited eye disorders that result in the gradual deterioration of retinal function. The retina is made up of light-sensing cells and it lines the inside of the eye. The role of specialized retinal cells, called photoreceptors, is to convert light into electrical signals. These signals are transmitted to the brain to be interpreted as images. In RP, these cells slowly die, resulting in loss of vision.
The first symptom of RP is night blindness, this is followed by a decrease in peripheral (side) vision and eventually, central vision may be affected. The symptoms of RP appear at different ages, and the rate of progression varies considerably from individual to individual.
Usher syndrome is caused by defects (mutations) in certain genes that are necessary for normal vision and hearing. It is inherited as an autosomal recessive trait. This means that an affected child usually inherits one copy of a defective gene from each parent. The parents may not know they are carriers because they have no symptoms of the disease. When both parents are carriers, there is a one in four chance with EACH pregnancy that the child will be affected.
There are many subtypes of Usher syndrome, each of which is presumably caused by at least one different gene. So far, researchers have discovered and characterized only two of the responsible genes: one for a form of type 1 and another for a form of type 2. Blood testing may be available if a patient has one of these specific subtypes. If an abnormality in the gene is found, then testing could be performed on other relatives to identify carriers.
At this time, there are no scientifically proven treatments to halt the progress of Usher syndrome. Researchers are hard at work finding the genes that contribute to Usher syndrome and it is hoped that this knowledge will provide the basis for treatments and cures.
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We would like to keep you updated with the latest news and updates, fill out the registration form to stay in touch.This information is provided by:
Alex V. Levin, M.D., MHSc., FRCSC
Ophthalmologist
The Hospital for Sick Children, Toronto
Medical Advisor, The Foundation Fighting Blindness - Canada
This information has been provided by The Foundation Fighting Blindness - Canada and has been reviewed by its medical advisor. It is not intended to replace the advice of a qualified vision care professional. The Foundation urges everyone affected by an eye disorder to seek the best healthcare possible.