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Original Articles

Hearing loss features in GJB2 biallelic mutations and GJB2/GJB6 digenic inheritance in a large Italian cohort

, , , , , , , & show all
Pages 12-17 | Received 10 Oct 2007, Published online: 07 Jul 2009
 

Abstract

The aim of this study was to describe the clinical features of hearing loss due to mutations on connexin 26/30 coding genes (GJB2/GJB6). Mutations in the GJB2 gene are found to account for approximately 50% of cases of autosomal recessive non-syndromic deafness. Several European studies have estimated that the GJB2 healthy carrier condition involves about 2–4% of the population, with the 35delG mutations being the most common. A 342-kb deletion truncating the GJB6 gene (encoding connexin-30) has been associated with autosomal recessive non-syndromic deafness, mostly as digenic inheritance of the Cx30 deletion/Cx26 mutation. The following retrospective study describes audiological features and genotypes of a large cohort of 376 Italian hearing-impaired patients who underwent genetic screening for the GJB2/GJB6 genes and received follow-up care at our centre between January 2002 and October 2006. Sixteen different genotypes causing deafness in more than 27% of patients with either biallelic mutations or digenic inheritance GJB2/GJB6 were identified. The most frequent mutations were 35delG, M34T, L90P, and R184P.

Abbreviations
ABR=

Auditory brainstem response

EcochG=

Electrocochleography

PTA=

Pure-tone average

Abbreviations
ABR=

Auditory brainstem response

EcochG=

Electrocochleography

PTA=

Pure-tone average

Sumario

El objetivo de este estudio fue describir los rasgos clínicos de una pérdida auditiva debida a mutaciones de los genes codificadores de conexina 26/30 (GJB2/GJB6). Se encontró que las mutaciones en el gen GJB2 representan aproximadamente el 50% de los casos de sordera autosómica recesiva no sindrómica. Varios estudios italianos han estimado que la condición de portador GJB2 saludable involucra cerca del 2–4% de la población, siendo la mutación 35delG la más común. Un deleción 342-kb que trunca el gen GJB6 (codificador de conexina-30) ha sido asociado con la sordera autosómica recesiva no sindrómica, sobre todo como herencia digénica la deleción Cx30/mutación Cx26. El siguiente estudio retrospectivo describe los rasgos audiológicos y los genotipos de una gran cohorte de 376 pacientes hipoacúsicos que se sometieron a un tamiz genético para los genes GJB2/GJB6 y recibieron cuidados de seguimiento en nuestro centro entre enero 2002 y octubre 2006. Se identificaron dieciséis genotipos diferentes causando sordera en más del 27% de los pacientes con mutaciones bialélicas o de herencia digénica GJB2/GJB6. Las mutaciones más frecuentes fueron 35delG, M34T, L90P y R184P.

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