On this page:
- What Is Usher Syndrome?
- How is Usher syndrome inherited?
- How is Usher syndrome diagnosed?
- Is genetic testing for Usher syndrome available?
- National Eye Institute Research
- Medical Literature
This information was developed by the National Eye Institute (NEI) to help patients and their families in searching for general information about Usher syndrome. An eye care professional who has examined the patient's eyes and is familiar with his or her medical history is the best person to answer specific questions.
What Is Usher Syndrome?
Usher syndrome is an inherited condition that causes 1) a serious hearing loss that is usually present at birth or shortly thereafter and 2) progressive vision loss caused by retinitis pigmentosa (RP). RP is a group of inherited diseases that cause night-blindness and peripheral (side) vision loss through the progressive degeneration of the retina, the light-sensitive tissue at the back of the eye that is crucial for vision.
Researchers have described three types of Usher syndrome-type I, type II and type III.
- Individuals with Usher syndrome type I are nearly or completely deaf and experience problems with balance from a young age. They usually begin to exhibit signs of RP in early adolescence.
- Individuals with Usher syndrome type II experience moderate to severe hearing impairment, have normal balance, and experience symptoms of RP later in adolescence.
- Individuals with Usher syndrome type III are born with normal hearing but develop RP and then progressive hearing loss.
How is Usher syndrome inherited?
The Usher syndrome types are inherited as an autosomal recessive trait. This means that an affected person receives one abnormal gene from each of his or her parents. A person who inherits a gene from only one parent will be a carrier, but will not develop the disease.
A person with Usher syndrome must pass on one disease gene to each of his or her children. However, unless the person has children with another carrier of Usher genes, the individual's children are not at risk for developing the disease. Currently we cannot reasonably test everyone for carrier status, but this may change in the years ahead.
How is Usher syndrome diagnosed?
Since individuals with Usher syndrome have both hearing and visual symptoms, we perform testing of both systems. This testing includes:
- visual function tests: visual fields and electroretinogram (ERG)
- a retinal examination
- hearing tests
- balance tests for all patients age ten years and older
Although some of the genes that cause Usher syndrome have been identified, the diagnosis is still based on ocular and clinical testing.
Is genetic testing for Usher syndrome available?
At this time, genetic testing for Usher syndrome is done only as part of research projects. This is due to many factors. Usher syndrome is not caused by only one gene. So far, 10 Usher genes have been mapped: 7 for type I, 3 for type II, and 1 for type 3. There are still more genes to find. A few of these genes have been sequenced and described. These are MYO7A, harmonin, CDH23, PCDH15, all causing type I. The usherin gene causes type II disease.
Finding the genes is a very important advance in the fight against Usher syndrome. Further study is required to characterize these genes, and determine how the mutated genes cause Usher syndrome. Additional genes that cause Usher syndrome also need to be identified. Several researchers throughout the world are working on Usher syndrome. Findings from this research may one day allow treatments for Usher syndrome to be developed.
National Eye Institute Research
Researchers at of the National Eye Institute have been following individuals with Usher syndrome (Research Protocol # 93-EI-0161.) They are available for patient examination and consultation. The vision and hearing of each patient is evaluated. In addition, samples of blood from each patient are studied to better understand the genes involved in Usher syndrome. Patients interested in participating in this research study should contact:
Meira R. Meltzer, MA, MS
National Eye Institute
Resources can be found in the National Eye Institute's Eye Health Organizations Database.
For additional information, you may also wish to contact a local library.
For information on your topic, you may wish to conduct a search of the medical literature. The National Library of Medicine (NLM) coordinates PubMed, a computerized medical literature database. You can conduct your own free literature search by accessing PubMed through the Internet. For help on how to search PubMed and how to get journal articles, please see PubMed Help. You may also get assistance with a literature search at a local library.
Please keep in mind that articles in the medical literature are usually written in technical language. We encourage you to share articles with a health care professional who can help you understand them.