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About 1 in 1000 British children are born deaf.1 Although the true genetic contribution to the aetiology is unknown, it is estimated that genetic causes account for at least 60% of cases.2 Of genetic cases, 70% of deafness occurs in the absence of other clinical features and is termed “non-syndromic”. Recessive genes account for 80% of such deafness, which represents about one-third of all hereditary deafness. At the time of writing, 33 recessive non-syndromal deafness genes have been mapped and 17 have been identified.3 Despite this genetic heterogeneity, sequence variations in the connexin26 (or gap junction beta-2, GJB2) gene account for up to 50% of cases of non-syndromic, prelingual, sensorineural hearing loss in some populations.4,5 Connexin26 mutations account for 17% of severe and 30% of moderate, non-syndromal deafness in the UK.6 Its contribution to hearing loss world wide is variable, but the 35delG allele alone accounts for approximately 10-20% of cases of hearing loss in white people of northern European descent, and approximately 30–40% of cases in Mediterranean regions.5 The heterozygote frequency of 35delG varies from 1-3% in white populations of north European origin, and is about 1 in 30 in those of Mediterranean descent.5
Connexin26 testing is now available for affected subjects and their families on a diagnostic basis in the United States and Europe, and its use in prenatal genetic counselling is being piloted in Greece.7 Antenatal screening for connexin26 mutations alone is unlikely to be considered in the UK as only a minority of non-syndromic deafness would be detected.6 However, as advances in mutation screening technology such as gene chips take place, it is possible that carrier screening for a wider number of recessive deafness genetic variants may become technically feasible within the next few years. Such …