Usher Syndrome
Usher syndrome is the major cause of deaf-blindness.
It's a relatively rare genetic disorder that is characterised by a moderate to profound deafness at birth or shortly after, and gradual vision loss due to retinitis pigmentosa (RP), a degeneration of the retinal cells.
Researchers believe that the hearing loss in Usher syndrome is due to a problem with the sensory cells in the inner ear that prevents sound signals from being transmitted to the brain. The vision loss is caused by a degeneration of the retina, usually starting off as night blindness, then leading to tunnel vision and can then progress to complete blindness.
Types of Usher Syndrome
There are three forms of Usher syndrome:
People with Usher syndrome type I are born profoundly deaf and have problems with their balance. They usually begin to show the first signs of RP in adolescence.
People with Usher syndrome type II are usually hard of hearing rather than deaf and their hearing doesn't deteriorate over time. Their balance is usually normal. Symptoms of RP develop in early adulthood.
With Usher syndrome type III, people aren't born deaf but experience a gradual loss of hearing and vision. They may or may not have difficulties with their balance.
Type I and II are the more common forms. Type III is significant in only a few areas such as Finland and Birmingham, England.
How is Usher Syndrome inherited?
Usher Syndrome is genetically passed through families, and both parents must be carriers. Each parent has one gene with the disease, paired with one gene that is normal. When children are conceived they will inherit genes in one of four ways.
- 1. If they get the two healthy genes from the parents, they do not have the condition and are not carriers.
- 2&3. If they get a disease gene from one parent and not the other, they will be carriers but not have the symptoms.
- 4. If they get the two disease genes from their parents, they will have the condition.
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