What causes Usher syndrome?

Usher syndrome is an inherited disease causing deafness and blindness. Both parents must have the gene that causes the condition in order for a child to inherit it. Parents can be carriers, meaning they have no symptoms, to pass along the gene. If both parents are carriers, the child has a 25 percent chance of having it, a 50 percent chance of carrying it, and a 25 percent chance of being unaffected.
The night-vision loss is caused by retinitis pigmentosa, which causes the degeneration of the retina of the eye.