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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.
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Other Resources
Individuals with Usher syndrome may find the following
organizations useful for more information on the disease and
rehabilitation:
National Eye Institute
2020 Vision Place
Bethesda,
MD 20892-3655
(301) 496-5248
2020@nei.nih.gov
http://www.nei.nih.gov
The Foundation Fighting Blindness
Executive Plaza 1,
Suite 800
11350 McCormick Road
Hunt Valley, MD 21031-1014
1-800-683-5555
TDD: 1-800-683-5551
(410) 785-1414
TDD : (410) 785-9687
http://www.blindness.org
Funds research to discover the causes, treatments,
preventions, and cures for retinitis pigmentosa, macular
degeneration, Usher syndrome, and other related retinal
degenerations.
American Association of the Deaf-Blind
814 Thayer
Avenue, Room 302
Silver Spring, MD
20910
1-800-735-2258
TTY: (301) 588-6545
http://www.tr.wou.edu/dblink/aadb.htm
Encourages
independent living for individuals who are deaf-blind. Provides
technical assistance to persons who are deaf-blind, families,
educators, and service providers.
DB-LINK: National Information Clearinghouse on Children Who
are Deaf-Blind
345 N Monmouth Avenue
Monmouth, Oregon
97361
1-800-438-9376
TTY: 1-800-854-7013
http://www.tr.wosc.osshe.edu/dblink/index.htm
Offers
information that assists education, medical, and service personnel
in providing comprehensive services infants, toddlers, children,
and youth who are deaf-blind in the U.S.
Helen Keller National Center for Deaf-Blind Youths and
Adults
111 Middle Neck Road
Sands Point, NY
11050
(516) 944-8900
TTY: (516) 944-8637
http://www.helenkeller.org/
Seeks
to enable each person who is deaf-blind to live and work in his or
her community of choice. Provides a comprehensive vocational
rehabilitation training program.
National Family Association for Deaf-Blind
111 Middle
Neck Road
Sands Point, New York 11050
1-800-255-0411, ext.
275
TTY: (516) 944-8637
http://www.nfadb.org/
Serves as the largest national network of families focusing on
issues surrounding deaf blindness.
National Institute on Deafness and Other Communication
Disorders (NIDCD)
31 Center Drive, MSC 2320
Bethesda, MD
20892-2320
(301) 496-7243
TTY: (301) 402-0252
http://www.nidcd.nih.gov/
Conducts
and supports research on diseases and disorders affecting hearing,
balance, smell, taste, voice, speech, and language.
For additional information, you may also wish to contact a local
library.
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