Usher syndrome is a rare, inherited disorder that involves loss
of hearing and sight. Hearing loss is due to the inability of
the auditory nerves to send sensory input to the brain. This is
called sensorineural hearing loss. The vision loss, called
retinitis pigmentosa (RP), usually happens after age ten. RP is
a deterioration of the retina. The retina is a layer of light-
sensitive tissue that lines the back of the eye. It changes
visual images into nerve impulses in the brain that allow us to
see. RP slowly gets worse over time. Three types of Usher
syndrome have been identified: types I, II, and III. The age of
onset and severity of symptoms separate the different types.
Usher syndrome is caused by a genetic mutation. A child must
inherit one defective gene from each parent in order to develop
Usher syndrome. A child with one defective gene is a carrier and
will not have any symptoms. It is not clear what causes the
mutation in the gene. The only known factor that increases the
risk of Usher syndrome is hav