CONNEXIN 26 HEARING LOSS

Connexin 26 Hearing Loss — the single most common cause of genetic deafness worldwide, where the GJB2 genotype predicts cochlear implant performance and carrier screening can prevent unexpected hearing loss in the next generation.

Whole genome sequencing identifies all GJB2 variants and the linked GJB6 deletions that cause digenic hearing loss — providing the molecular diagnosis that predicts audiological trajectory and cochlear implant candidacy.

GJB2
GJB6

About this condition

Connexin 26 Hearing Loss

Pathogenic variants in GJB2 (connexin 26, chromosome 13q12.11) are the most common cause of non-syndromic sensorineural hearing loss worldwide, accounting for approximately 50% of autosomal recessive hereditary deafness and approximately 20-30% of all genetic hearing loss. GJB2 encodes connexin 26, a gap junction protein essential for potassium recycling in the cochlea — the process that maintains the endocochlear potential required for hair cell mechanotransduction. Carrier frequency is approximately 1 in 25-35 in most populations — comparable to or higher than CFTR (cystic fibrosis) carrier frequency.

The most common GJB2 pathogenic variant in European populations is c.35delG (35delG), accounting for approximately 70% of disease alleles. In East Asian populations, c.235delC predominates; in Ashkenazi Jews, c.167delT. Over 300 GJB2 pathogenic variants have been reported. Hearing loss in biallelic GJB2 is typically congenital, bilateral, sensorineural, and stable (non-progressive) — distinguishing it from SLC26A4-related hearing loss which is characteristically progressive and fluctuating. Severity ranges from mild to profound depending on the specific variant combination: two truncating variants typically cause severe-to-profound loss; compound heterozygosity with missense variants may produce mild-to-moderate loss.

Cochlear implantation outcomes in GJB2-related deafness are excellent — typically superior to outcomes for other causes of deafness — because the pathology is limited to the cochlear gap junction system while the spiral ganglion neurons (which the cochlear implant stimulates) are preserved. This genotype-outcome correlation directly influences cochlear implant candidacy and timing decisions. Additionally, GJB6 (connexin 30) deletions on the same chromosome can cause hearing loss in trans with a single GJB2 variant (digenic inheritance) — explaining some cases of apparent monoallelic GJB2 hearing loss.

Cochlear implant outcomes are superior in GJB2-related deafness compared to most other causes — spiral ganglion neurons are preserved. This genotype-outcome data directly influences cochlear implant candidacy and timing.

Gene locus: GJB2 (13q12.11), GJB6 (13q12.11)

GJB2 carrier frequency of 1 in 25-35 is one of the highest for any recessive disease gene. Universal carrier screening identifies at-risk couples before the birth of a deaf child — enabling immediate neonatal intervention.

1 in 25-35 people carry a GJB2 variant — universal carrier screening identifies more at-risk couples than any gene-specific panel

At a carrier frequency of approximately 1 in 30, approximately 1 in 900 couples are both GJB2 carriers, and approximately 1 in 3,600 births will have GJB2-related hearing loss. Despite being more common than cystic fibrosis, GJB2 is not included in most commercial carrier screening panels. Whole genome sequencing identifies GJB2 carrier status alongside all other carrier genes in a single comprehensive evaluation, enabling preconception counseling and immediate newborn hearing intervention planning for identified carrier couples.

GJB6 deletions cause digenic hearing loss with GJB2 — explaining 'missing' second alleles in apparent GJB2 carriers

Approximately 5-10% of patients with hearing loss who carry a single GJB2 pathogenic variant have a large deletion in GJB6 (connexin 30) on the homologous chromosome — a digenic or contiguous gene deletion mechanism. Standard GJB2 sequencing-only panels classify these patients as 'carriers' rather than affected individuals, missing the molecular diagnosis. Whole genome sequencing detects both GJB2 sequence variants and GJB6 structural deletions from the same dataset, resolving the complete connexin hearing loss genotype.

Connexin 26 Hearing Loss — the single most common cause of genetic deafness worldwide, where the GJB2 genotype predicts cochlear implant performance and carrier screening can prevent unexpected hearing loss in the next generation.

Connexin 26 Hearing Loss

GJB2 carrier frequency of 1 in 25-35 is one of the highest for any recessive disease gene. Universal carrier screening identifies at-risk couples before the birth of a deaf child — enabling immediate neonatal intervention.

1 in 25-35 people carry a GJB2 variant — universal carrier screening identifies more at-risk couples than any gene-specific panel

GJB6 deletions cause digenic hearing loss with GJB2 — explaining 'missing' second alleles in apparent GJB2 carriers

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