USH1C-related disorders are a group of conditions linked to hearing loss, with or without vision loss. These disorders don’t affect intelligence or cause other major health problems.
One type of USH1C-related disorder is called Usher syndrome type 1C. Usher syndrome has three types (I, II, and III) categorized by the severity of the disease and when symptoms appear. Mutations in USH1C lead to Usher syndrome type 1, which brings about hearing loss, balance issues, and progressive vision loss. In Usher syndrome type 1C, babies are born profoundly deaf in both ears. They also experience balance problems, leading to delayed development. These children might start sitting and walking later than usual and struggle with sensing changes in speed or direction. By childhood or early adolescence, they develop retinitis pigmentosa (RP), an eye disease causing night blindness and gradual peripheral vision loss. Some may develop cataracts, further affecting vision. In some cases, central vision is impaired, leading to blindness in a few individuals. Certain mutations in USH1C are also linked to DFNB18A, a type of isolated hearing loss. Unlike Usher syndrome, DFNB18A doesn’t affect movement or balance. While there’s no cure for USH1C-related disorders, early treatment is crucial for a child’s language development. Cochlear implants may help regain some hearing, and sign language is a good communication option. For those with vision loss, visual aids and specialized instruction are helpful.
As noted above, these conditions are caused by pathogenic (disease-causing) variants in the USH1C gene and exhibits autosomal recessive inheritance. This means that both parents must be carriers to have a 25% chance to have a child with the condition. The risk of being a carrier is based on a person’s ancestry or ethnic background. For example, individuals of Sephardic Jewish descent have a 1 in 125 chance to be a carrier.