One study showed that in the New York City area, 0.7% of Ashkenazi Jews are carriers of a particular mutation, which would mean that 1.2 in 100,000 Ashkenazi Jewish children would be affected. Type 3 is more common in Finland and among Ashkenazi Jews. Usher syndrome type 3 is rare, making up just 2% of all cases of Usher syndrome. The disease does not affect intelligence nor does it cause any other health problems. Some problems may arise later in life, however. Unlike other forms of Usher syndrome, type 3 does not usually cause major problems with balance. Often by mid-life, the person is legally blind. Peripheral (side) vision is often the first to be reduced. Often arising during puberty, this causes night blindness that progresses to blind spots in the late teens or early adult years. Usher syndrome type 3 causes an eye disease known as retinitis pigmentosa. By middle age, they are often completely deaf. People with Usher syndrome type 3 are born with normal hearing and most commonly develop hearing loss in their teenage years, requiring hearing aids by mid- to late-adulthood. In some people, the hearing and/or vision loss can be profound, while in others it can be milder. The rate at which hearing and vision decline varies greatly from person to person, even among those in the same family. Usher syndrome type 3 is an inherited disease that causes progressive hearing loss and vision impairment.
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