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RESEARCH PRODUCT

<i>GJB2</i> Mutations and Genotype-Phenotype Correlation in 335 Patients from Germany with Nonsyndromic Sensorineural Hearing Loss: Evidence for Additional Recessive Mutations Not Detected by Current Methods

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We report on 335 patients (319 families) with mild-to-profound nonsyndromic sensorineural hearing loss. We identified 178 mutated <i>GJB2</i> alleles representing 29 different sequence changes (including 3 novel mutations: Q7P, N14D, H100Q), and 2 alleles with the deletion del(GJB6-D13S1830) of the <i>GJB6</i> gene. Eleven <i>GJB2</i> mutations (119 mutated alleles) were truncating (T), and 18 mutations (59 alleles) were nontruncating (NT). Biallelic <i>GJB2</i> mutations were found in 71 patients (21.2%; 67 families; 25 different genotypes). Audiograms of 62 patients (56 families) with biallelic <i>GJB2</i> mutations typically indicated a profound hearing loss with T/T mutations, moderate hearing loss with T/NT mutations, and mild hearing impairment with NT/NT mutations (p < 0.01, Student’s t test). From 37 patients (34 families) with biallelic <i>GJB2</i> mutations, audiograms at different ages were available and indicated progressive hearing loss (>15 dB) in 10 patients (27.0%, 10 families). Interestingly, we identified an unexpectedly large subset of patients (n = 29; 8.7%) presenting with only one <i>GJB2</i> mutation (n = 14 T/wild-type; n = 15 NT/wild-type). This strongly suggests the presence of additional recessive mutations that are not detected by current <i>GJB2</i> mutation and <i>GJB6 </i>deletion analyses.