What is genetic hearing loss and deafness?
Some types of deafness can be inherited. In the UK, about one in 1,600 children is born moderately to profoundly deaf because they inherit a mutated gene.
What types of gene mutation cause deafness?
The chances of developing deafness caused by a mutated gene depends on whether the mutated gene is dominant or recessive.
Dominant gene mutation
Where a dominant gene mutation causes hearing loss, the affected gene can come from the mother or the father. The chance of passing on this mutation to your children is one in two. But dominant genes don't have the same effect on everyone. In the same family, a gene can cause profound deafness in one person and mild deafness in another. Sometimes, it may not affect a person’s hearing at all.
A dominant gene mutation may have been in the family for generations. Alternatively, it can sometimes appear for the first time in a family without a history of deafness.
Recessive gene mutation
Where a recessive gene mutation causes deafness, both the mother and father must have passed on an affected gene to their child. If the child only inherits one copy of the affected gene from one parent, they'll be a 'carrier'. This means that though they are hearing themselves, they can pass on the affected gene to their children.
A person whose deafness is due to a recessive mutation may have parents who are hearing. They may also have brothers and sisters who are both hearing and deaf, and no family history of deafness – even though the deafness is genetic in origin.
What are mitochondrial genes?
Most of our genes are located on chromosomes, but some are found in structures called mitochondria in the cells of our bodies. Mitochondria are inherited from our mothers only. This means that if deafness is caused by a mutation in a mitochondrial gene, only women can pass on deafness to their children, although both men and women can have this type of deafness.
Why is genetic information helpful?
If you are deaf or if deafness runs in your family, genetic information may be helpful:
- to find out the chances of having a child who is deaf
- to try to identify the cause of your deafness
- to look for medical conditions that might be associated with your deafness. About 30% of deafness in young children is associated with other medical conditions or ‘syndromes. These additional conditions are usually of no concern, but it may be important to identify some. For example, someone with Usher syndrome has deafness from birth and loses their sight gradually.
How can I get genetic information?
If you would like information about genetics and deafness, you will need to have a consultation in a genetic clinic. This consultation is often known as ‘genetic counselling’. Genetic counselling is free on the NHS but you will need to get a referral from your GP, paediatrician, ENT consultant or audiological physician
There are about 30 NHS centres offering genetic counselling for deafness around the country.
What are the benefits of genetic research into deafness?
In the future, many more genes needed for hearing may be discovered. The genes discovered so far mainly cause deafness in childhood or young adulthood. However, deafness in older people – hearing loss due to ageing or presbycusis – can have an inherited component too. Researchers are beginning to discover which genes contribute to hearing loss due to ageing. This knowledge might make it possible to identify people at risk of losing their hearing. They may then be able to change their lifestyle to protect it.
What is Action on Hearing loss doing?
Find out about our fund cutting-edge research around the world into treatments and cures for hearing loss.