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Usher syndrome

Usher syndrome is a genetic disease causing deaf-blindness. It is essentially progressive retinitis pigmentosa combined with congenital hearing impairment. It is almost always inherited in an autosomal recessive pattern and is estimated to occur in 1 in 10,000 people. Whilst this is a rare genetic condition, it represents the major cause of syndromic deafness with blindness. The condition gets its name from British ophthalmologist, C.H. Usher, who in 1914 wrote a paper describing several cases in which the link between congenital deafness and retinitis pigmentosa was stressed. more...

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Usher syndrome is divided into three types, I, II and III. Children with type I syndrome are born profoundly deaf, and eyesight usually begins degrading after the first decade of life, beginning with night-blindness. If identified at a young age, children usually receive a cochlear implant, and generally learn spoken language. Sign language is also sometimes used, though when vision loss becomes severe one must revert to tactile signing. Problems with balance are usually present, due to the failure of the hair cells of the inner ear. Type II children are hard-of-hearing, and changes in sight usually begin later, first becoming noticeable after the second decade of life. In the type III syndrome, hearing loss as well as retinitis pigmentosa can occur later in life.

Usher syndrome I

Worldwide, the estimated prevalence of Usher syndrome type I is 3 to 6 per 100,000 people in the general population.

Mutations in the CDH23, MYO7A, PCDH15, Usher 1C (also known as Harmonin), and USH1G (now identified as SANS) genes cause Usher syndrome type I. Usher syndrome type I can be caused by mutations in one of several different genes. These genes function in the development and maintenance of inner ear structures such as hair cells (stereocilia), which transmit sound and motion signals to the brain. Alterations in these genes can cause an inability to maintain balance (vestibular dysfunction) and hearing loss. The genes also play a role in the development and stability of the retina by influencing the structure and function of both the rod photoreceptor cells and supporting cells called the retinal pigmented epithelium. Mutations that affect the normal function of these genes can result in retinitis pigmentosa and vision loss.

Usher syndrome II

Usher syndrome type II occurs at least as frequently as type I, because type II may be underdiagnosed or more difficult to detect, it could be up to three times as common as type I.

Mutations in the MASS1 (also called VLGR1) and USH2A genes cause Usher syndrome type II. Usher syndrome type II may be caused by mutations in any of three different genes, two of which have been identified to date. These genes are called USH2A and MASS1. Usherin, the protein made by the USH2A gene, is located in supportive tissue in the inner ear and retina. Usherin is critical for the proper development and maintenance of these structures, which may help explain its role in hearing and vision loss. The precise function of the protein made by the MASS1 gene is not yet known.

Usher syndrome III

The frequency of Usher syndrome type III is highest in the Finnish population, but it has been noted rarely in a few other ethnic groups.

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Usher Syndrome
From Pamphlet by: National Institute on Deafness and Other Communication Disorders, 4/1/99

* What is Usher syndrome?

* Who is affected by Usher syndrome?

* What causes Usher syndrome?

* What are the types of Usher syndrome?

* What are the characteristics of the three types of Usher syndrome?

* How is Usher syndrome diagnosed?

* How is Usher syndrome treated?

* What research is being conducted on Usher syndrome?

* Where can I get additional information?

What is Usher syndrome?

Usher syndrome (US) is the most common condition that involves both hearing and vision problems. A syndrome is a disease or disorder that has more than one feature or symptom. The major symptoms of US are hearing impairment and an eye disorder called retinitis pigmentosa, in which vision worsens over time. Some people with US also have balance problems. There are three different types of US. Although it was first described by Albrecht Von Graefe in 1858, US was named for Charles Usher, a British eye doctor, who believed that this condition was inherited or passed from parents to their children.

Who is affected by Usher syndrome? [up arrow]

More than half of the estimated 16,000 deaf-blind people in the United States are believed to have US.

What causes Usher syndrome? [up arrow]

US is inherited or passed from parents to their children through genes. Genes are located in every cell of the body and contain the instructions that tell cells what to do. Some genes specify traits such as hair color. Other genes are involved in the development of body parts, such as the ear. Still others determine how parts of the body work. Each person inherits two copies of each gene; one gene comes from each parent. Sometimes genes are altered or mutated. Mutated genes may cause cells to act differently than expected.

US is passed along in families by autosomal recessive inheritance, which requires two copies of the US gene before the disorder is seen. Each parent of a child with US usually has one standard and one mutated US gene. A child with US receives two mutated genes, one from each parent. Usually parents are unaware that they have or carry a US gene. This is because they would need two of the mutated genes in order to have signs of US. Presently, at least eight different genes are thought to cause the various types of US.

What are the types of Usher syndrome? [up arrow]

The three types of US are called US type 1 (US1), US type 2 (US2), and US type 3 (US3). US1 and US2 are the most common types of US. Together, US1 and US2 account for approximately 10 percent of all cases of children who are born deaf.

What are the characteristics of the three types of Usher syndrome?

People with US1 are profoundly deaf from birth and have severe balance problems. Many of these individuals obtain little or no benefit from hearing aids. Most use sign language as their primary means of communication. Because of the balance problems, children with US1 are slow to sit without support and rarely learn to walk before they are 18 months old. These children usually begin to develop vision problems by the time they are ten. Visual problems most often begin with difficulty seeing at night, but tend to progress rapidly until the individual is completely blind.

Those with US2 are born with moderate to severe hearing impairment and normal balance. Although the severity of hearing impairment varies, most of these children perform well in regular classrooms and can benefit from hearing aids. These children most commonly use speech to communicate. Retinitis pigmentosa, which is a degeneration of the retina or the part of the eye that receives images of objects, is characterized by blind spots that begin to appear shortly after the teenage years. The visual problems in US2 tend to progress more slowly than the visual problems in US1. When an individual's vision deteriorates to blindness, his or her ability to read speech from the lips is lost.

Children born with US3 have normal hearing and normal to near-normal balance. Hearing worsens over time. Children develop noticeable hearing problems by their teenage years and usually become deaf by mid to late adulthood. Retinitis pigmentosa in the form of night blindness usually begins sometime during puberty. Blind spots appear by the late teenage years to early adulthood. By mid adulthood, the individual is usually blind.

How is Usher syndrome diagnosed? [up arrow]

Hearing loss and retinitis pigmentosa are rarely found in combination. Therefore, most people who have retinitis pigmentosa and hearing loss probably have US1 or US2. Special tests such as electronystagmography (ENG) to detect balance problems and electroretinography (ERG) to detect retinitis pigmentosa help doctors to detect US early. Early diagnosis is important in order to begin special educational training programs to help the individual deal with the combined hearing and vision difficulties.

How is Usher syndrome treated?

Presently, there is no cure for US. The best treatment involves early identification in order to begin educational programs. The exact nature of these educational programs will depend on the severity of the hearing and vision impairments as well as the age and abilities of the individual. Typically individuals will benefit from adjustment and career counseling; access to technology such as hearing aids, assistive listening devices or cochlear implants; orientation and mobility training; and communication services and independent living training that may include Braille instruction, low vision services, or auditory training.

What research is being conducted on Usher syndrome?

The current emphasis of US research is locating the genes that cause the syndrome and identifying the function of those genes. This research will lead to improved genetic counseling and early diagnosis, and may eventually expand treatment options. Scientists are also developing mice that have the same characteristics as humans who have the various types of US. Mouse models will make it easier to determine the function of the various genes involved in US. Research is also being conducted to improve the early identification of children with the syndrome. Treatment strategies such as the use of cochlear implants for hearing impairment and intervention strategies to alleviate retinitis pigmentosa are also being examined.

Where can I get additional information? [up arrow]

For more information, contact the NIDCD Information Clearinghouse.

[up arrow] National Institute on Deafness and Other Communication Disorders National Institutes of Health 31 Center Drive, MSC 2320 Bethesda, MD USA 20892-2320 www.nih.gov/nidcd

Send technical comments and questions to webmaster@nidcd.nih.gov

Voice (301) 496-7243; TTY (301) 402-0252; Fax (301) 402-0018

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