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Usher Syndrome Type I.

Authors

Lentz J1, Keats BJB2.

Source

GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2019.
1999 Dec 10 [updated 2016 May 19].

Author information

1
Neuroscience Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, Louisiana
2
Department of Genetics (Emeritus), Louisiana State University Health Sciences Center, New Orleans, Louisiana

Excerpt

CLINICAL CHARACTERISTICS:

Usher syndrome type I is characterized by congenital, bilateral, profound sensorineural hearing loss, vestibular areflexia, and adolescent-onset retinitis pigmentosa. Unless fitted with a cochlear implant, individuals do not typically develop speech. Retinitis pigmentosa (RP), a progressive, bilateral, symmetric degeneration of rod and cone functions of the retina, develops in adolescence, resulting in progressively constricted visual fields and impaired visual acuity.

DIAGNOSIS/TESTING:

The diagnosis of Usher syndrome type I is established in a proband using electrophysiologic and subjective tests of hearing and retinal function. Identification of biallelic pathogenic variants in one of six genes – MYO7A, USH1C, CDH23, PCDH15, USH1G, and CIB2 – establishes the diagnosis if clinical features are inconclusive.

MANAGEMENT:

Treatment of manifestations: Hearing aids are usually ineffectual; cochlear implantation should be considered, especially for young children. Communication skills may be optimized if all (i.e., including unaffected) family members receive specialized training from educators of the hearing impaired. Progressive vision loss may eventually limit communication to tactile signing. Surveillance: Routine ophthalmologic evaluation to detect potentially treatable complications such as cataracts. Agents/circumstances to avoid: Competition in sports requiring acute vision and/or good balance may be difficult and possibly dangerous; progressive loss of peripheral vision impairs the ability to safely drive a car. Because of the high risk for disorientation when submerged in water, swimming needs to be undertaken with caution. Evaluation of relatives at risk: The hearing of at-risk sibs should be assessed as soon after birth as possible to allow early diagnosis and treatment of hearing loss.

GENETIC COUNSELING:

Usher syndrome type I is inherited in an autosomal recessive manner. At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Carrier testing for at-risk relatives and prenatal testing for pregnancies at increased risk are possible if the pathogenic variants in the family are known.

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