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.
If you are deaf or if hearing loss runs in your family, genetic information may help identify the cause of your condition. It may also identify whether you are likely to have a child who is deaf.
The chances of developing deafness caused by a mutated gene depends on whether the gene is dominant or recessive.
Dominant gene mutation
A dominant gene mutation that causes hearing loss can come from the mother or the father. The chance of passing on this mutation to your children is one in two.
Dominant genes don’t have the same effect on everyone. In one 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 a family for generations, but it can also appear for the first time in a family without a history of deafness.
Recessive gene mutation
A recessive gene mutation that causes deafness in a child must have been passed on by both the mother and father.
If the child only inherits one copy of the affected gene from one parent, they’ll be a carrier. This means that although they can hear, they can pass on the affected gene to their own children.
A person who is deaf 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.
Mitochondrial gene mutation
Most of our genes are in our chromosomes, but some are found in structures called mitochondria.
Mitochondria are in the cells of our bodies and are inherited from our mothers. This means that if deafness is caused by a mutation in a mitochondrial gene, only women can pass on deafness to their children. However, both men and women can have this type of deafness.
Genetic information and deafness
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
- try to identify the cause of your deafness
- 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. For example, someone with Usher syndrome has deafness from birth and loses their sight gradually.
How to get genetic information
You can get information about genetics and deafness by having a consultation in a genetic clinic. This consultation is called genetic counselling.
Genetic counselling is free on the NHS, but you need to be referred by your GP, paediatrician, ear, nose and throat (ENT) consultant or audiologist.
Genetic research into deafness
In the future, many more genes may be discovered that are needed for hearing. The genes discovered so far mainly cause deafness in childhood or young adulthood.
However, deafness in older people could be due to genetic inheritance too. Researchers are beginning to discover which genes cause age-related hearing loss. This might mean people who are at risk of losing their hearing can be identified, and can take steps to protect their hearing.