The distinction between the types is made primarily by severity of hearing loss, presence or absence of vestibular function, and onset of vision loss. As can be seen in Table 1, the types are further divided into distinct molecular subgroups. Kimberling, personal communication, 2009), and there are three phenotypic or clinical presentation types generally recognized. For a brief overview of the more common syndromic hearing losses, see Keats (2002).Īlthough it is highly heterogenic, there are least 10 genes that cause Usher syndrome (W. While many syndromes may be identified clinically, this strategy has resulted in a significant delay in the diagnosis of Usher syndrome. Genetic testing is available for many disorders and presents ethical and economic challenges for today's practitioner. Our understanding of, and ability to test for, the underlying etiology of syndromes has been greatly enhanced by the study of the human genome and proteins necessary for normal development. When hearing loss is accompanied by other clinical findings, it is often classified as a syndrome, and there are more than 400 such syndromes outlined by Gorlin, Torell, and Cohen (1995). Autosomal recessive inheritance pattern where both parents are unaffected carriers (N = normal, r = recessive trait).
Obviously, carriers of two differing Usher genes will produce additional carriers but no affected offspring.įigure 1. Kimberling, personal communication, 2009), but because there are many different genetic versions of Usher syndrome there is only a small chance of a specific carrier mating with an identical carrier. Estimates are that 1 in 10 persons carries some form of recessive gene for Usher syndrome (W. The parents are surprised by the diagnosis and frequently respond that it cannot be genetic because it is not in their family. For this reason, you will rarely see families with a history of Usher syndrome. As can be seen in Figure 1, when both parents are asymptomatic carriers of the Usher syndrome gene, they have a 25% chance with each pregnancy of producing a child with Usher syndrome. Because it is autosomal recessive, all forms of Usher syndrome are inherited from not one but both parents.
Usher syndrome is named after Charles Usher, a British ophthalmologist who described the nature of the disease in 1914. This article is aimed at increasing audiologists' understanding of the audiologic and visual presentation, diagnostic criteria, and intervention strategies involved with Usher syndrome. Therefore, audiologists are in a position to improve differential diagnosis outcomes for children with Usher syndrome. Because of newborn hearing screening, audiologists are often the family's primary contact. So, while parents learn of their child's hearing loss relatively early, without a differential diagnosis they proceed with critical decisions related to intervention, communication, and educational options unaware that their child will eventually be blind. Newborn hearing screening has reduced the age of identification of children with hearing loss from 12–18 months to 6 months or less (Harrison & Rousch, 1996), but the diagnosis of Usher syndrome, with its devastating vision loss, typically lags 5–10 years behind the identification of the hearing loss (Kimberling & Lindenmuth, 2007).
Although considered a rare disease, it is the most frequent cause of deaf-blindness in humans. Usher syndrome is a genetic condition involving sensorineural hearing loss and retinitis pigmentosa (RP).
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