High frequency hearing loss correlated with mutations in the GJB2 gene

Genetic hearing impairment affects approximately 1/2000 live births. Mutati ons in one gene, GJB2, coding fur connexin 26 cause 10%-20% of all genetic sensorineural hearing loss. Mutation analysis ill the GJB2 gene and audiolo gy were performed on 106 families presenting with at least one child with c ongenital hearing loss. The families were recruited from a hospital-based m ultidisciplinary clinic, which functions to investigate the aetiology of se nsorineural hearing loss in children and which serves an ethnically diverse population. In 74 families (80 children), the aetiology was consistent wit h non-syndromic recessive healing loss. Six different connexin 26 mutations , including one novel mutation, were identified. We show that GJB2 mutation s cause a range of phenotypes from mild to profound hearing impairment and that loss of heating in the, high frequency range (4000-8000 Hz) is a chara cteristic feature in children with molecularly diagnosed connexin 26 hearin g impairment. We also demonstrate that this type of audiology and high freq uency hearing loss is found in a similar-sized group of deaf children in wh om a mutation could only be found ill one of the connexin 26 alleles, sugge sting connexin 26 involvement in the aetiology of hearing loss in these cas es. In our study of the M34T mutation, only compound heterozygotes exhibite d hearing loss, suggesting autosomal recessive inheritance.