Genetic mutations account for approximately 50% of congenital hearing loss (HL), and about 80% of genetic deafness is nonsyndromic, usually autosomal recessive. Mutations of the GJB2 gene, encoding the connexin 26 protein (Cx26), account for about 50% of nonsyndromic autosomal recessive deafness in some populations. Most past studies of the etiology have been performed in schools for children with deafness or in specialty clinics. Currently over 40 states in the United States have established newborn hearing screening (NHS) programs, providing opportunity to investigate the etiology in a population-based cohort. Three states, Utah, Rhode Island, and Hawaii, are collaborating in a CDC-funded investigation of HL etiology ascertained through state programs. The study's aims are to (1) classify the causes of congenital HL; (2) determine the frequency of GJB2 and two mitochondrial mutations; and (3) identify issues that surround linking genetic services with NHS and follow-up (EHDI). Participants with confirmed permanent HL are offered a comprehensive medical genetics evaluation and testing for GJB2 and the mitochondrial mutations. To date, 170 probands and immediate family members have been evaluated. We have identified 39 with syndromic HL, 89 patients with nonsyndromic bilateral sensorineural (SN) HL, and 42 with conductive, acquired, or unilateral SN. Sixteen of the cases (18% of nonsyndromic SN) were found to have biallelic mutations in GJB2. One mitochondrial mutation has been found in this population, but it is likely not the cause of the hearing loss in that case. This multistate investigation is the first to determine the causes of HL in a population ascertained through NHS. The results of this study could help facilitate the incorporation of clinical genetic services into EHDI. Determining the etiology of HL is important in patient management, and detection of GJB2 mutations may preclude other diagnostic testing.
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