Retina0208.jpg
Photograph of the retina of a patient with Usher syndrome (left) compared to a normal retina (right). The optic nerve (arrow) looks very pale, the vessels (stars) are very thin and there is characteristic pigment, called bone spicules (double arrows).


Nature of the Genetic Difficulty

Ushers Disease is inherited in an autosomal* recessive pattern, which means both copies of the gene in each cell have mutations. The parents of the individual with an autosomal recessive condition, each carry one copy of the mutated gene, however, may never show signs or symptoms of the disease.
  • (Autosomal meaning the mutated gene is not located on either of the chromosomes that determine the persons sex.)
  • (Recessive meaning that in order for someone to have Usher's Syndrome, the person must recieve the mutated gene from each parent.)
Mutations that cause Ushers Syndrome are: CDH23, CLRN1, GPR98, MYO7A, PCDH15, USH1C, and USH2A. These related genese are responsible for providing instructions for making proteins that play the important roles of normal hearing, balance and vision.
If a child is born with the Usher's Syndrome gene AND a normal gene, then they are predicted to have both normal hearing and vision. If both of the parents are carriers of the mutated gene for Usher's Syndrome, they will have a one in four chance of having a child with Usher's Syndrome with each birth. Usually parents with normal hearing and vision, do not know that they are carriers of the Usher's Syndrome gene. Its currently not possible to determine whether someone is a carrier of the Usher's gene, especially if their family has no history of it.
"Because Usher syndrome affects hearing, balance, and vision, diagnosis of the disorder usually includes the evaluation of all three senses. Evaluation of the eyes may include a visual field test to measure a person’s peripheral vision, an electroretinogram (ERG) to measure the electrical response of the eye's light-sensitive cells, and a retinal examination to observe the retina and other structures in the back of the eye. A hearing (audiologic) evaluation measures how loud sounds at a range of frequencies need to be before a person can hear them. An electronystagmogram (ENG) measures involuntary eye movements that could signify a balance problem" (National Institute on Deafness and Other Disorders).
When two carriers of the Usher's Syndrome gene have a child together they have:
-A 1 in 4 chance of having a child with Usher's Syndrome.
-A 2 in 2 chance of having a child who is a carrier of the Usher's Syndrome mutated gene.
-A 1 in 4 chance of having a child who is neither born with Usher's Syndrome or carries the gene for it.

Basis Facts of Disease

There are three types of Usher's Syndrome:
Type 1-Children born with type 1 Usher's Syndrome are deaf at birth and have severe balancing problems. Hearing aids have little to no benifit for kids with type 1. "If a child is diagnosed with type 1 Usher syndrome early on, before he or she loses the ability to see, that child is more likely to benefit from the full spectrum of intervention strategies that can help him or her participate more fully in life's activities" (NICID). Children usually develop vision problems in early childhood, and almost always before the age of 10. Vision problems begin with the difficulty to see at night but then progresses to the point of total blindness.
Found on genes: MY07A, USH1C, CDH23, PCDH15, SANS.
Type 2-Children are born with moderate to severe hearing loss and normal balance. Most of these children benefit from hearing aids and can communicate orally. Vision problems tend to progress slower in type 2 than in type 1.
Found on genes: USH2A, VLGR1 and WHRN
Type 3-Children are born with normal hearing. Although born with the disorder and have normal balance, children may develop balance problems later on. Hearing and sight worsen over time;night vision problems usually begins sometime during puberty, which escalates to blind spots which start to occur during late teens early adult hood, then finally by mid-adult hood, have complete blindness.
Found on gene: USH3A

Prognosis

Currently there is no cure for Usher's Syndrome. The best treatment involves early identification so that educational programs can begin as soon as possible; however, how much help these programs can give to someone with Usher's Syndrome, depends on the severity of it.
Treatments that are typically offered, range from:
-Hearing Aids
-Assistive Learning Devices
-Cochlear Implants
-ASL (American Sign Language)
Some treatments or help go as far as, independent living-training that include brail instruction, low-vison services and auditory training.
"Some ophthalmologists believe that a high dose of vitamin A palmitate may slow, but not halt, the progression of *retinitis pigmentosa. This belief stems from the results of a long-term clinical trial supported by the National Eye Institute and the Foundation for Fighting Blindness" (National Institute on Deafness and other Communication Disorders). However, this idea is still under close experimentation; has not been fully recommended yet to patients with Usher's Syndrome.
  • Retinitis Pigmentosa:degeneration of the retina manifested by night blindness and gradual loss of peripheral vision, eventually resulting in tunnel vision or total blindness.

Sources Cited

National Institute on Deafness and Other Communication Disorders http://www.nidcd.nih.gov/health/hearing/usher.asp
Google: Usher's Syndrome http://www.google.com
New York Online Access to Health http://www.noah-health.org/en/genetic/
Dictionary http://dictionary.reference.com/browse/retinitis+pigmentosa
Laboratory Directory http://www.genetests.org/