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HEARING LOSS is extremely common and can present at any time from infancy to old age. About one in 1000 infants has profound hearing impairment, with half thought to be of genetic origin. Many deafness genes exist, but the most common cause of hearing loss in American and European populations is a mutation in the connexin 26 (Cx26) gene. Cx26 has a carrier rate of 3%, similar to that for cystic fibrosis, and it causes about 20% of childhood deafness.
Mutations in Cx26 cause congenital syndromic and nonsyndromic deafness - that is, the deafness is not accompanied by other symptoms, such as blindness. Cx26 is located on chromosome 13q11-12 and codes for a gap junction protein called connexin 26. Gap junctions are plasma membrane channels that allow the movement of small molecules and ions between adjacent cells. Gap junctions of the inner ear may play a role in maintaining potassium homeostasis, which is important for inner-ear function and, thus, hearing. It has been proposed that mutations in Cx26 may disrupt potassium circulation and result in deafness.
The discovery that Cx26 mutations are a cause of congenital hearing loss can help in the early diagnosis of hearing impairment. Early identification and management of deafness is important for the development of language and social skills.
Revised May 1, 2000
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