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Usher Syndrome

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Overview

Usher syndrome is a genetic disorder characterised by the loss of both hearing and vision. It is the most common form of inherited deaf-blindness, accounting for approximately 50% of such cases and affecting somewhere between 4 to 17 out of every 100,000 individuals.[1] Named after Charles Usher, the Scottish ophthalmologist who first examined the disease’s pathology in detail, the syndrome results from a combination of retinitis pigmentosa (RP), which leads to gradual vision loss, and abnormalities in the inner ear, which lead to hearing loss. The inner ear abnormalities consist of damage to the sensory receptor cells—or “hair cells”—leading to what is referred to as “sensorineural” hearing loss. The structure of the inner ear, called the cochlea, is not able to detect sound and send the appropriate information to the brain.

Vision loss takes a similar form for patients with Usher syndrome: as in other forms of RP, the photoreceptor cells gradually die off and are no longer able to effectively send visual information to the brain. The rod photoreceptors typically die off first, resulting in a loss of the peripheral vision they are responsible for; this leads eventually to the loss of cone photoreceptors, which are responsible for central, high-acuity vision. The experience of vision loss for patients is often described as a progressively worsening form of tunnel vision.

The disease is subdivided into three types, with type 1 being the most severe and type 3 being least—a breakdown of symptoms associated with each type is provided below under “Symptoms and Diagnosis.” Mutations in at least six genes can lead to Usher syndrome type 1 (the most common being the genes MYO7A and CDH23); mutations in at least three genes can lead to type 2 (USH2A is the most common); and mutations in the CLRN1 gene leads to type 3.[2] In all cases, the mutations obstruct the production of proteins that are central to the development and function of cells that communicate information to the brain: in the case of hearing, hair cells, and in the case of sight, photoreceptors.

Content on this page was written by Dr. Chad Andrews and Dr. Mary Sunderland, and was most recently updated on August 23, 2018. An earlier version of the content was approved by Dr. Patrick Yang and Dr. Bill Stell.

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