Usher syndrome is a genetic condition that causes hearing loss, vision loss, and sometimes balance/vestibular problems. Usher syndrome is "recessive" which means that two of the same Usher genes must be inherited - one from the mother, one from the father - in order for the child to have Usher syndrome. Often, parents do not know that they are carriers of the Usher syndrome gene because there is no history of Usher syndrome in the family.
When both parents are carriers of the same Usher gene, there is a 25% chance that their child will have Usher syndrome, a 50% chance that their child will be a carrier of the Usher gene, and a 25% chance that their child will neither be a carrier nor have Usher syndrome. If both parents have Usher syndrome caused by the same gene, all of their children will have Usher syndrome. Some families have two or more children with Usher syndrome.
For more information about the genetics of Usher syndrome, you may view our USH Talk, "Genetics 101."