Genetic study of autosomal recessive nonsyndromic sensorineural hearing loss in Kuwaiti children

Abstract

EnAbstract Background The prevalence of congenital hearing loss was found to be one in 1000 of live births. Fifty percent of the cause is genetic and autosomal recessive nonsyndromic sensorineural hearing loss (ARNSNHL) is responsible for 80% of the genetic causes. Study design Descriptive cross-sectional study. Objectives To study the genetic causes of ARNSNHL, mainly mutation in the gene encoding connexin26 (Cx26), and to correlate the identified gene and mutation with the degree and configuration of hearing loss, the progressiveness of hearing loss, as well as its relation to language development. Patients and methods One hundred children, age ranging from 6 months to 18 years, presenting with congenital ARNSNHL were chosen. Behavioral observation audiometry or pure tone audiometry to identify the hearing threshold level of the children was performed. Imittancemetry, otoacoustic emissions, auditory brainstem response, and computed tomography scan study were also undertaken. In addition, genetic tests to detect Cx26 mutations using a PCR and primers, as well as sequencing using different primers were also undertaken. Results Out of the total of 100 cases, 15 children were shown to have positive results for Cx26; nine of these were heterozygous and six were homozygous. Twelve participants (80%) among the Cx26 cases were due to 35delG. Out of the nine children who were heterozygous, six showed positive results for D1 (35delG), whereas three children were found to have positive results for D2 (G2A at location base 71). All the six homozygous cases were shown to be positive for D1 (35delG). Thus, the results revealed that 80% of the positive genetic results cases had 35delG. Conclusion Eighty percent of the cause of ARNSNHL in a Kuwaiti population was the 35delG mutation and 20% was due to G2A at location base 71. Of all the cases, 57% showed a positive family history of hearing loss. The homozygous cases presented with more severe clinical pictures compared with the heterozygous cases.