Moreover, the subtype USH2B, which has not been confirmed, was also excluded. The subtype USH1A, previously identified and described in published papers, is no longer considered responsible for the syndrome and does not exist anymore therefore, it was excluded from this review. USH is the most common cause of syndromic hearing loss after Pendred syndrome and is categorized into three clinical types with 14 subtypes, following causative mutations in different genes and loci. Nonsyndromic recessive and dominant hearing loss without retinopathy caused by USH genes has also been reported. In addition, PDZD7, a modifier gene, is considered responsible for Usher type 2 when associated with mutations in other Usher genes, such as USH2A, ADGRV1, and WHRN. Other genes and loci have been related to the disease however, their roles are not clear and must be confirmed in further studies: ESPN (USH1M), HARS (USH3), CEP78 (atypical Usher), CEP250 (atypical Usher), ABDH12 (USH3), and ARSG (atypical Usher), and three loci, namely, USH1E, USH1H, and USH1K. USH is inherited in an autosomal recessive pattern, and to date, nine causative genes have been identified and confirmed: MYO7A, USH1C, CDH23, PCDH15, and SANS for Usher type 1 USH2A, ADGRV1, and WHRN for Usher type 2 CLRN1 for Usher type 3.ĬIB2 (USH1J) is no longer considered responsible for Usher syndrome and was recently excluded from Usher genes by Booth et al., 2018 ( accessed on 21 December 2021). It takes its name from the ophthalmologist Charles Usher, who described a large series of 69 affected patients from 40 families with hearing loss and retinopathy. It is a genetic condition that includes hearing loss, retinopathy (retinitis pigmentosa), and vestibular areflexia with different entities and onset. Usher syndrome (USH) is the most common deaf–blind syndrome, with 50% of deaf-blindness in persons younger than 65 years of age. It affects social life, communication, access to information, orientation, and the ability to move around freely and safely. Thus, deaf-blindness is a distinct disability that limits activities and restricts participation in society. Deaf-blindness is a combined vision and hearing impairment of such severity that it is difficult for the impaired senses to compensate for each other. The use of our “near senses”-smell, taste, and tactility-essentially becomes important when hearing and vision are impaired. Human communication is, to a large extent, based on our “far senses”: hearing and vision. This narrative review reports the causative forms, diagnosis, prognosis, epidemiology, rehabilitation, research, and new treatments of USH. Digenic, bi-allelic, and polygenic forms have also been reported, in addition to dominant or nonsyndromic forms of genetic mutations. USH is inherited in an autosomal recessive pattern. To date, nine causative genes have been identified and confirmed as responsible for the syndrome when mutated: MYO7A, USH1C, CDH23, PCDH15, and USH1G (SANS) for Usher type 1 USH2A, ADGRV1, and WHRN for Usher type 2 CLRN1 for Usher type 3. USH has been grouped into three main clinical types: 1, 2, and 3, which are caused by mutations in different genes and are further divided into different subtypes. The syndrome was first described by Albrecht von Graefe in 1858, but later named by Charles Usher, who presented a large number of cases with hearing loss and retinopathy in 1914. Balance disorders and bilateral vestibular areflexia are also observed in some cases. Usher syndrome (USH) is the most common genetic condition responsible for combined loss of hearing and vision.
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