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Usher syndrome type 3a11/27/2023 Usher syndrome is responsible for the majority of deaf-blindness. (See the article on human genetics for more details.) The genes implicated in Usher syndrome are described below. "Recessive" means that both parents must contribute an appropriate gene for the syndrome to appear, and "autosomal" means that the gene is not carried on one of the sex chromosomes (X or Y), but rather on one of the 22 other pairs. Usher syndrome is inherited in an autosomal recessive pattern. Animal models of this human disease (such as knockout mice and zebrafish) have been developed recently to study the effects of these gene mutations and to test potential cures for Usher syndrome. First recognized in the 19th century, Usher syndrome was the first condition to demonstrate that phenotypes could be inherited in tandem deafness and blindness are inherited together, but not separately. Since Usher syndrome mutations are recessive, consanguinity of the parents is a risk factor. If both parents have Usher syndrome in the same gene, all their children are overwhelmingly likely to have the same condition by contrast, the children of a mixed marriage (one parent with Usher syndrome and the other with wild-type genes) are overwhelmingly likely to not have the condition, although they will be all asymptomatic carriers. ![]() Thus, both males and females are equally likely to inherit Usher syndrome. Usher syndrome is inherited in an autosomal recessive pattern, meaning that the mutated gene is not found on a sex chromosome ( autosomal) and that the syndrome only appears in people in whom both copies of the gene are mutated ( recessive). The three subtypes correspond to different mutations: Usher syndrome I and II are associated with a mutation in any one of six or three different genes, respectively, whereas only one mutation has been linked with Usher III. Usher syndrome is an inherited disorder associated with a mutation in any one of roughly 10 genes. In some cases, the foveal vision is spared, leading to "doughnut vision" central and peripheral vision are intact, but there is an annulus around the central region in which vision is impaired. In other cases, there is early degeneration of the cone cells in the macula, leading to a loss of central acuity. Usually, the rod cells of the retina are affected first, leading to early night blindness and the gradual loss of peripheral vision. The qualifier pigmentosa reflects the fact that clumps of pigment may be visible by an ophthalmoscope in advanced stages of degeneration. The gradual vision loss of this syndrome is associated with retinitis pigmentosa, which is a degeneration of the retinal cells. People with Usher syndrome III are not born deaf, but experience a gradual loss of their hearing and vision they may or may not have balance difficulties. ![]() ![]() People with Usher II are also born deaf, but do not seem to have noticeable problems with balance they also begin to lose their vision later (in the second decade of life) and may preserve some vision even into middle age. They also exhibit balance difficulties and learn to walk slowly as children, due to problems in their vestibular system. People with Usher I are born profoundly deaf, and begin to lose their vision in the first decade of life. Usher syndrome has three clinical subtypes, denoted as I, II and III in decreasing order of severity. Usher syndrome is incurable at present, but preliminary experiments with gene therapy in mice are promising. The word syndrome means that multiple symptoms occur together, in this case, deafness and blindness. Other names for Usher syndrome include Hallgren syndrome, Usher-Hallgren syndrome, rp-dysacusis syndrome and dystrophia retinae dysacusis syndrome. Usher syndrome (sometimes referred to as " Usher's syndrome") is a relatively rare inherited condition that is a leading cause of deaf-blindness.
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