Usher syndrome is a rare genetic disorder causing individuals to go deaf and blind, and in some cases to lose vestibular control. The severity of the vision, hearing, or balance loss depends on the type of Usher one has. With an estimated 50,000 people with Usher syndrome in the U.S. alone, it is considered the leading cause of combined deaf/blind disorders worldwide. It is passed to offspring by both parents, who each contain a copy of the mutated gene. Those who inherit only one copy of the mutated gene are considered to be carriers and do not express symptoms of the disorder. However, carriers can pass the mutated gene on to their children as well.
Usher syndrome is characterized by 3 major symptoms…
Vision loss in Usher syndrome is due to retinitis pigmentosa (RP), a degenerative condition of the retina. The retina is a delicate tissue in the back of the eye composed of light sensing photoreceptor cells called rods and cones. Rods and cones are responsible for converting light into electrical impulses that transfer messages to the brain but deteriorate over time in those with Usher syndrome.
Hearing loss due to Usher syndrome is adversely affected by the same mechanism that causes cells to die in the retina. These nerve cells are found in the cochlea, a sound transmitting structure of the inner ear.
Balance relies heavily on the two vital senses of vision and hearing. In some cases of Usher syndrome, the vestibular function is completely absent. As such, vestibular issues are frequently found in those with Usher syndrome.