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Excerpts: Mutations in GJB2 are the most common cause of moderate-to-profound congenital inherited deafness in the midwestern United States. This deafness etiology (requiring deafness-causing mutations of both alleles) was found in 18 (35%) of 52 probands evaluated for congenital, moderate-to-profound sensorineural hearing loss (Table 1) and in more than 50% of multiplex sibships. Although numerous deafness-causing mutations of this gene occur, a single mutation, 35delG, predominates. Our data are consistent with other national and international data in showing that 60% of persons with GJB2-related deafness are homozygous for the 35delG allele.13, 14, 16 The carrier rate as a mean (SE) in the general population for this allele is 2.5% (0.66%) (Table 3). The total carrier rate for all GJB2 deafness-causing mutations is 3.01% (probable range, 2.54%-3.56%). The corresponding predicted prevalence of GJB2-related congenital hearing loss is 22.7 (probable range, 15.1-31.9) per 100,000 births. More than two thirds of these individuals have profound or severe-to-profound hearing loss, although there can be phenotypic variability in the degree of loss even within the same family. The lower 35delG carrier rates noted by Scott et al21 (1/100; P=.31) and Kelley et al16 (2/96; P=.58) (P values represent comparison with our results) are consistent with stochastic variances due to smaller sample sizes. The study by Morell et al23 showed a carrier rate of 1 in 173 among white college students. Although the difference between this result and our results does not achieve statistical significance (P>.09), it is important to note that the predicted prevalence of 35delG homozygosity corresponding to this carrier rate would be 0.8:100,000, a value inconsistent with observed data.1-4, 14-16
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