GJB2-related conditions are a group of conditions caused by variations in the GJB2 gene, with similar overlapping symptoms.
DFNB1 non-syndromic hearing loss - also called connexin 26 - affects people's ability to hear but does not affect any other part of the body. It can be caused by variations in several genes, including GJB2. People affected by this condition are born with mild to profound hearing loss, caused by damage to structures in the inner ear (sensorineural). This generally does not worsen over time. The seriousness of the hearing loss can vary, even among members of the same family.
Certain variations in the GJB2 gene may also cause autosomal dominant (AD) syndromic deafness. This means a variation in only one copy of the GJB2 gene can cause symptoms. AD syndromic deafness causes mild to profound hearing loss and skin symptoms, including thickened, dry or scaly skin, and changes to the hair, nails and teeth.
All GJB2-related conditions do not affect intelligence, and early intervention to improve social and educational outcomes can be helpful.
|Alternative Names:||Bart-Pumphrey syndrome, connexin 26, DFNB1 nonsyndromic hearing loss and deafness, syndrome, hystrix-like ichthyosis with deafness (HID), palmoplantar keratoderma with deafness (PPK), Vohwinkel syndrome, keratitis-ichthyosis-deafness (KID) syndrome, autosomal dominant nonsyndromic deafness (DFNA3)|
As humans we have about 23,000 genes. These genes are like tiny instruction manuals that influence our health, growth and development. We inherit half of our genes from our biological mum and the other half from our biological dad. These genes are lined up on structures called chromosomes. Most of us have 23 pairs of chromosomes. The first 22 pairs are called autosomes and for the most part - these are the same among men and women. The 23rd pair determine our sex - two X chromosomes for a female and one X and one Y chromosome for males.
GJB2-related conditions (including DFNB1 nonsyndromic hearing loss and deafness) is known as an autosomal recessive condition. For autosomal recessive conditions, if a person has a variation in one copy of their gene, they are a carrier. This means that they are healthy because they also have a working copy of the gene. But, they can still pass their non-working copy to their child.
If the other parent also happens to be a carrier of the same gene, there is a 25% (1 in 4) chance that they both pass this gene variation on to their child — and as such, have a child affected by the disease.
If both parents are carriers of GJB2-related conditions (including DFNB1 nonsyndromic hearing loss and deafness), there’s a one in four chance that their children could develop symptoms.
Carrier testing is like a checkup for your genes. It tests to see if you carry a gene variation that could cause a serious genetic disease in your child. Eugene offers an inclusive genetic carrier screening panel that includes GJB2-related conditions (including DFNB1 nonsyndromic hearing loss and deafness), but there's a total 301 conditions that can be tested.
Eugene’s carrier test is a clinical grade test that can be done from the comfort of your own home — it’s just a saliva test. You're also paired with a genetic counsellor who provides mindful support and guidance every step of the way.Learn more about carrier screening
The biggest benefit of screening for GJB2-related conditions (including DFNB1 nonsyndromic hearing loss and deafness) is that it can help future parents understand their reproductive risk so they can be ready and empowered to make more informed decisions. If neither partner are carriers, it provides reassurance and peace of mind that the risk of having a child with a genetic disease is low.
Since 90% of children that have a recessive genetic disease like GJB2-related conditions (including DFNB1 nonsyndromic hearing loss and deafness) had no previous family history of it, it often feels completely out of the blue for the parents. Getting screened is a way to know this risk in advance, which can help familes manage or even prevent the disease in the first place.