| Institution: | 1. Department of Otolaryngology, National Hospital Organization Tokyo Medical Center, Tokyo, Japan;2. Laboratory of Auditory Disorders, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan;3. Division of Otorhinolaryngology, Chiba Children''s Hospital, Chiba, Japan;4. Department of Otorhinolaryngology, National Center for Child Health and Development, Tokyo, Japan;5. Department of Otolaryngology, Mejiro University Clinic, Saitama, Japan;6. Department of Otolaryngology, Saitama Children''s Medical Center, Saitama, Japan;g Department of Otorhinolaryngology, National Hospital Organization Mie Hospital, Mie, Japan;h Department of Otorhinolaryngology, Kobe Children''s Hospital, Hyogo, Japan;i Department of Otolaryngology, National Hospital Organization Ureshino Medical Center, Saga, Japan;j Department of Otolaryngology, National Hospital Organization Nagasaki Medical Center, Nagasaki, Japan;k Department of Otolaryngology, Kobari General Hospital, Chiba, Japan;l Department of Otolaryngology, Kanto Rosai Hospital, Kanagawa, Japan;m National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan;n Department of Otolaryngology, Mita Hospital, International University of Health and Welfare, Tokyo, Japan |
| Abstract: | The hearing loss caused by GJB2 mutations is usually congenital in onset, moderate to profound in degree, and non-progressive. The objective of this study was to study genotype/phenotype correlations and to document 14 children with biallelic GJB2 mutations who passed newborn hearing screening (NHS). Genetic testing for GJB2 mutations by direct sequencing was performed on 924 individuals (810 families) with hearing loss, and 204 patients (175 families) were found to carry biallelic GJB2 mutations. NHS results were obtained through medical records. A total of 18 pathological mutations were identified, which were subclassified as eight inactivating and 10 non-inactivating mutations. p.I128M and p.H73Y were identified as novel missense GJB2 mutations. Of the 14 children with biallelic GJB2 mutations who passed NHS, eight were compound heterozygotes and 3 were homozygous for the c.235delC mutation in GJB2, and the other three combinations of non-c.235delC mutations identified were p.Y136X-p.G45E/p.V37I heterozygous, c.512ins4/p.R143W heterozygous, and p.V37I/p.R143W heterozygous. These 14 cases demonstrate that the current NHS does not identify all infants with biallelic GJB2 mutations. They suggest that the frequency of non-penetrance at birth is approximately 6.9% or higher in DFNB1 patients and provide further evidence that GJB2 hearing loss may not always be congenital in onset. |
