Usher Syndrome

What is Usher syndrome?

Usher syndrome is a genetic condition characterised 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.

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 colour). 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, MASS1, 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 are carriers of one copy of the altered gene but do not show signs and symptoms of the disorder.

What other names do people use for Usher syndrome?

  • Deafness-retinitis pigmentosa syndrome
  • dystrophia retinae pigmentosa-dysostosis syndrome
  • Graefe-Usher syndrome
  • Hallgren syndrome
  • Retinitis pigmentosa-deafness syndrome
  • Usher's syndrome

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