Usher syndrome is an inherited condition characterized by hearing impairment and progressive vision loss. Balance may also be affected. Symptoms vary from person to person and progress at different rates.
There are at least three different forms of Usher syndrome. People with Usher syndrome type 1 (USH1) are born completely deaf and experience problems with balance. The first signs of RP - night blindness and loss of peripheral vision - usually appear in early adolescence.
In Usher syndrome type 2 (USH2), newborns have moderate to severe hearing impairment. Symptoms of RP typically start shortly after adolescence. Visual problems progress less rapidly than in Usher type 1 and hearing loss usually remains stable.
A rarer third type of Usher syndrome (USH3) was documented in 1995. Children with USH3 are usually born with good or only mild impairment of hearing. Their hearing and vision loss is progressive, starting around puberty. Balance may be affected.
Hearing loss in Usher syndrome is due to a genetic mutation (alteration) affecting nerve cells in the cochlea, a sound-transmitting structure of the inner ear. The same genetic defect also adversely affects photoreceptor cells in the retina, leading to vision loss. Recently, scientists have discovered that some Usher syndrome genes code for proteins that support cilia, fingerlike projections found on many cells, including photoreceptors and cochlea cells. This may explain why one individual may have both vision and hearing problems.
For another disease where damage to cilia may be causing visual impairment paired with problems in another system, see Bardet-Biedl Syndrome.