Non-syndromic Hearing Loss: GJB2 / GJB6 Analysis

Diagnostic Use

The incidence of congenital, prelingual hearing loss is approximately one in 1000 births. Of these, one in four are classified as non-syndromic. Defects in GJB2, which is located on the long arm of chromosome 13 and encodes the protein Connexin 26, are responsible for the most common form of non-syndromic sensorineural deafness type 1 (DFNB1).

DFNB1 is an autosomal recessive form of sensorineural hearing loss which results from damage to the neural receptors of the inner ear, the nerve pathways to the brain, or the area of the brain that receives sound information. Approximately 98% of affected individuals are homozygous or compound heterozygous for mutations in the GJB2 gene. The deletion of a single guanosine (G) residue within a stretch of six G’s at position 30-35 in the GJB2 gene (c.35delG) leads to premature chain termination and is present in 40-70% of DFNB1 patients (approximate population carrier frequency 1:40 to 1:100).

In a further 2% of DFNB1 patients, heterozygosity for a GJB2 mutation and a 342kb deletion affecting part of the GJB6 gene (encoding the Connexin 30 protein) is observed. A single mutation involving the splicing site of the non-coding exon 1 of GJB2 is an infrequently reported variant.


Genetics - Molecular Pathology

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Constituent Tests


Connexin 26 Gene Analysis
DFNB1 sequencing
GJB2 sequencing
GJB6 sequencing

Turnaround Time

4 weeks

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