There are three clinical types of Usher Syndrome:
- Type 1 – causes profound deafness. Poor balance is often associated with it which causes delay in the age of sitting and walking. Retinitis Pigmentosa may be noticed before the age of 10. People with this type of Usher usually prefer to communicate using sign language, and see themselves as deaf who are losing their vision.
- Type 2 – causes a moderate hearing loss and balance is not affected. RP may not become apparent until adolescence. Speech assisted by the use of lip-reading and hearing aids will usually be their first method of communication.
- Type 3 – is a rarer form of Usher syndrome. It does have a higher frequency in people of Finnish ancestry. Children usually have normal hearing and sight from birth, then develop a hearing loss and RP in adolescence or later. Hearing can deteriorate steadily over ten or fifteen years, and some people also experience balance problems.
There are at least eleven different genetic types of Usher syndrome, as determined by the genes that are involved. There are six different genes that cause Usher type 1, three that cause Usher type 2, and two that cause Usher type 3. One cannot determine the genetic type by clinical testing; DNA testing is the only reliable way of determining the true genetic type.
People and children with Usher type 1 are typically totally deaf whereas those with type 2 are usually hard of hearing. People with Usher type 1 also have balance problems that start from birth. This causes them to usually start walking later than most other babies. Children with type2 walk at the normal age of 10 to 14 months. The RP of Usher type I is often diagnosed earlier that that for type 2, though recent breakthroughs in genetic testing are allowing for earlier diagnosis of all types of Usher Syndrome
|
