Causes of deafness in British Bangladeshi children: a prevalence twice that of the UK population cannot be accounted for by consanguinity alone.

OBJECTIVE: To study the causes and prevalence of sensorineural deafness in Bangladeshi children resident in East London. METHODS: This was a cross sectional survey of children of Bangladeshi origin living in East London with bilateral sensorineural hearing loss of 40 db HL or more. In this study, 134 patients were included. The study looked primarily at the causes of sensorineural hearing loss in this population. RESULTS: The prevalence of deafness in Bangladeshi children in East London is approximately 3.86 per 1000 [95% confidence intervals (CI) 3.20, 4.65] which is significantly greater than the average UK prevalence of 1.65 per 1000. The prevalence of deafness in these Bangladeshi children belonging to non-consanguineous families only, the prevalence falls to 2.73 per 1000 (95% CI 2.19, 3.41). In 60% cases the cause of deafness was genetic. The single most common cause of sensorineural hearing loss in this population was mutations in the GJB2 gene (Connexin 26) in 20 of these patients (17%). Parents were consanguineous in 33% of the families. CONCLUSION: This study concludes that prevalence of sensorineural deafness in Bangladeshi children is at least 2.3 times the national average. This study also concludes that genetic causes are the common cause of deafness in this ethnic group, with nearly 30% of children with non-syndromic deafness having mutations in GJB2. Although parental consanguinity was very high in this population it did not account for the whole increase in prevalence.

Spectrum of GJB2 mutations causing deafness in the British Bangladeshi population.

OBJECTIVE: Mutations in Gap Junction Beta 2 (GJB2) (the gene encoding the protein Connexin 26) have been found to be a major cause of non-syndromic sensorineural recessive deafness. The mutations in GJB2 causing hearing impairment vary in different populations. The aim of this study was to determine the prevalence and spectrum of GJB2 mutations in prelingual deafness in a population of Bangladeshi origin in the UK. DESIGN: Cross-sectional survey. SETTING: Community based audiology clinic and tertiary level genetics department. METHODS: Fifty-three families (67 patients) with sensorineural hearing loss of unknown cause were included in the study. Detailed history and examination excluded syndromic and environmental causes of hearing loss in the subjects as far as possible. Genetic analysis was performed, specifically looking for mutations in the GJB2 gene. RESULTS: Of the 53 families, 14 were confirmed to have biallelic pathogenic mutations in GJB2 (26%). The most common mutations of GJB2 in this population were W24X, IVS1+1, M1V, W77X and Q124X, W24X being the most common mutation seen in 57% of patients. CONCLUSION: Mutations in GJB2 are responsible for over one quarter of non-syndromic sensorineural deafness in the British Bangladeshi population. It is recommended that all Bangladeshi patients with non-syndromic hearing loss should be first tested for GJB2 mutations before requesting other aetiological investigations.