Usher Syndrome

Usher Syndrome is the most common condition that involves both hearing and visual disturbances. Between 3–6 percent of deaf children or children with hearing impairment have Usher's, roughly four in 100,000 live births in the United States. Signs and symptoms include moderate to severe hearing impairment, retinitis pigmentosa, and normal to severe balance problems. Usher Syndrome was first described in Germany in the middle of the 19th century by Al-brecht Von Graefe but is named for Charles Usher, a British ophthalmologist who showed the inheritance pattern of this syndrome in 1914.

There are three types of Usher Syndrome; all passed by autosomal recessive inheritance. This indicates that both parents have a copy of the mutated gene and it was passed via a non-sex chromosome. USH1 is the most severe; children are born deaf or nearly deaf, have severe balance problems, and develop vision problems by the age of ten. USH2 is characterized by moderate to severe hearing impairment, [Page 1726]normal balance, and vision problems beginning in the teenage years. USH3 is highly variable. Typically children are born with normal hearing, most have normal balance, and characteristics of Usher's develop after puberty with blindness and deafness occurring in mid-adulthood.

The visual problems of Usher Syndrome are due to retinitis pigmentosa, a degeneration of the photoreceptor cells in the retina. There are two types of photoreceptor cells: rod cells and cone cells. Rod cells are for night vision and see objects in the periphery. Cone cells help distinguish fine detail and also perceive color.

The most common type of retinitis pigmentosa seen with Usher Syndrome is rod cell dystrophy. Patients will first note night blindness, followed by loss of peripheral vision with a progression toward tunnel vision; full blindness may or may not occur.

The diagnosis of Usher Syndrome is made by the combination of hearing impairment and retinitis pigmentosa. A full history and complete eye and hearing exam are important in making the diagnosis. Additional tests can be run for early detection, including electronystagmography (ENG) to assess balance and electroretinography (ERG) to detect retinitis pigmentosa.

Treatment options are limited, as there is no cure for Usher Syndrome. Vitamin A may slow the progression of retinitis pigmentosa. Hearing aids and cochlear implants are sometimes helpful, but not curative. The most important treatment is counseling, orientation and mobility training, as well as educational programs for anticipated lifestyle changes.

Research is underway to determine the exact gene(s) associated with Usher Syndrome. Twelve loci have been identified and seven of these contain proteins that have already been linked to Usher Syndrome. This knowledge will help with genetic counseling, early detection, and treatment for patients living with Usher Syndrome.