Usher Syndrome
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What is Usher syndrome?Usher syndrome is a genetic condition characterized by hearing loss and progressive vision loss. The signs and symptoms of Usher syndrome vary in their severity and age of onset; most are present from birth or shortly thereafter, while a few begin later in childhood or adolescence. Genetic changes are related to the following types of Usher syndrome. * Usher syndrome type I * Usher syndrome type II * Usher syndrome type III All types of Usher syndrome include progressive vision loss due to retinitis pigmentosa, a disorder that affects the retina (the part of the eye that detects light and color). Retinitis pigmentosa causes light-sensing cells in the retina to gradually deteriorate. Night vision loss begins first, followed by blind spots that develop in the side (peripheral) vision. These spots enlarge and merge into a doughnut shape, producing tunnel vision. Central vision is reduced and blurs; in some cases, it may be limited but sharp for many years. Cataracts may develop in the teenage years or in adulthood. In addition, some people with Usher syndrome type I or type III have balance problems due to a defect in the part of the inner ear that controls balance. How common is Usher syndrome?Usher syndrome is thought to be responsible for 3 percent to 6 percent of all childhood deafness and about 50 percent of deaf-blindness in adults. Usher syndrome type I is estimated to occur in at least 4.4 per 100,000 people. It may be more common in certain ethnic populations, such as Ashkenazi (central and eastern European) Jews and the Acadian population in Louisiana. The frequency of type II Usher syndrome is unknown, but it is believed to be more common than type I. Usher syndrome type III is found most frequently in the Finnish population and is rare in the general European and American populations. What genes are related to Usher syndrome?Mutations in the CDH23, GPR98, MYO7A, PCDH15, USH1C, USH1G, USH2A, and USH3A genes cause Usher syndrome. These eight genes play important roles in normal hearing, balance, and vision. They function in the development and maintenance of inner ear structures such as hair cells that help transmit sound and motion signals to the brain. These genes also play a role in the development and stability of the retina by influencing the structure and function of light-sensing cells called rods and cones. Mutations in any of the genes listed above can lead to a loss of hair cells in the inner ear and a gradual loss of rods and cones in the retina. Degeneration of these sensory cells causes the hearing loss, balance problems, and vision loss characteristic of Usher syndrome. How do people inherit Usher syndrome?This condition is inherited in an autosomal recessive pattern, which means two copies of the gene in each cell are altered. Most often, the parents of an individual with an autosomal recessive disorder each carry one copy of the altered gene but do not show signs and symptoms of the disorder.
Source: National Institutes of Health
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Research conducted at Hadassah University, Department of Ophthalmology has provided new information about retinitis pigmentosa
2007 FEB 27 -- Researchers detail in "Novel USH2A mutations in Israeli patients with retinitis pigmentosa and Usher syndrome type 2," new data in retinitis pigmentosa. In this recent report, researchers in Jerusalem, Israel conducted a study "To identify USH2A mutations in Israeli patients with autosomal-recessive Usher syndrome type 2 (USH2) and retinitis pigmentosa (RP). Patients from 95 families with RP and 4 with USH2 were clinically evaluated." "USH2A exons 2-72 were scanned for mutations using single-strand conformation and sequencing analyses. The frequency of novel missense changes was determined in patients and controls using restriction endonucleases. The analysis revealed 3 USH2A mutations, 2 of which are novel, in 2 families with USH2 and a large family (MOL0051) with both USH2 and RP. Compound heterozygotes for 2 null mutations (Thr80fs and Arg737stop) in MOL0051 suffered from USH2 while compound heterozygotes for 1 of the null mutations and a novel missense mutation (Gly4674Arg) had nonsyndromic RP. Our results support the involvement of USH2A in nonsyndromic RP and we report here of a second, novel, missense mutation in this gene causing autosomal-recessive RP. Possible involvement of USH2A should be considered in the molecular genetic evaluation of patients with autosomal-recessive RP," wrote N. Kaiserman and colleagues, Hadassah University, Department of Ophthalmology. The researchers concluded: "Understanding the mechanism by which different USH2A mutations cause either USH2 or RP may assist in the development of novel therapeutic approaches." Kaiserman and colleagues published their study in Archives of Ophthalmology (Novel USH2A mutations in Israeli patients with retinitis pigmentosa and Usher syndrome type 2. Archives of Ophthalmology, 2007;125(2):219-24). For additional information, contact N. Kaiserman, Hadassah-Hebrew University Medical Center, Dept. of Ophthalmology, Jerusalem 91120, Israel. Publisher contact information for the journal Archives of Ophthalmology is: American Medical Association, 515 N State St., Chicago, IL 60610, USA. Keywords: Israel, Jerusalem, Ophthalmology, Retinitis Pigmentosa, Usher Syndrome. This article was prepared by Life Science Weekly editors from staff and other reports. Copyright 2007, Life Science Weekly via NewsRx.com.
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