Genetics and deafness

The National Deaf Children’s Society (NDCS) recognises that the issue of deafness and genetics is an extremely sensitive one which gives rise to a wide range of emotions and opinions.

As the only national charity solely supporting the needs of almost 35,000 deaf children and their families in the UK, the NDCS believes that it should provide a clear statement on an issue of considerable importance to the families it represents. The following policy is intended to clarify the Society's position for the professionals working with deaf children and their families as well as the families themselves.

Agreed by NDCS Trustee Board, July 2006 

The National Deaf Children’s Society is an organisation of families, parents and carers which exists to enable deaf children to maximise their skills and abilities and works to facilitate this process by every possible means.

Deafness is not an illness or a life-threatening condition. Therefore, the Society believes that if support is provided and positive attitudes are fostered, the challenge of deafness can be a rewarding one for deaf children and their families. The Society is committed to empowering parents of deaf children to make informed choices, by providing impartial advice and information on all aspects of childhood deafness.

Just as children inherit features, such as hair or eye colour, from their parents, sometimes hearing loss is inherited. Most people have 23 pairs of chromosomes in each of their cells. These are microscopic structures that contain genes. One of each pair of chromosomes is inherited from the mother and the other from the father. Sometimes there is an alteration or  change in a particular gene that results in a different characteristic, for example hearing loss. The change in a gene can be called a ‘fault’ or ‘mutation’.

Genes can work in different ways. Sometimes a child only needs to inherit one faulty gene from either their mother or their father to have that particular characteristic (dominant inheritance). Sometimes the child would need to have the same faulty gene passed on from both parents in order to have the condition (recessive inheritance). There are other different patterns of genetic inheritance that are less common.

Some people are known as ‘carriers’. This is where they have the altered gene but do not have the characteristic. So a person who is a carrier for hearing loss would carry the altered gene, but would not have a hearing loss themselves.

Sometimes a gene mutation is a ‘one-off’ that simply occurred by chance. This means that, although the hearing loss has a genetic cause, it has happened for the first time in that person and has not been inherited. However, it could be passed onto future generations.
 
The field of genetics is wide and fast growing. The NDCS feels it is important to clarify our position regarding different areas of genetics and genetic research, in the following way.

The Society views as desirable any form of research into gene-based therapy that might allow parents the choice of reducing the impact of deafness on their deaf child’s social and educational development. We recognise that, if any form of gene-based therapy for deafness does become available in the future, the resulting improvement of hearing could possibly be more permanent than that afforded by cochlear implants or hearing aids. If this were to occur, it would pose different ethical dimensions to the choices involved; for most parents this will make the decision to use such an intervention method more complex.

Genetic counselling provides information and support for individuals and families who are or have a chance of being affected by a range of inherited conditions including hearing loss. Genetic counselling provides families with information about the cause of the condition, how it might affect the child and family in the future and, if the family wish to know, how likely they are to have another child with the same condition. Genetic counselling enables families to make informed decisions about their child, their child’s future and may help them when planning for their family.

Some families find it helpful to know whether the hearing loss and any other associated medical condition were inherited. Other families prefer to wait until their children are grown up and able to decide for themselves.

If appropriate1 and the family would like to, the NDCS believes that families should be offered the chance to discuss their situation with their local Clinical Genetics (genetic counselling) team and should be referred by the doctor in charge of their child’s audiological care.

Families with a deaf child may be offered a genetic test. This involves the child and possibly other family members having a blood test. The blood sample is used to look for a gene or genes known to be involved with hearing loss.

In about 50% of children with a permanent hearing loss, their deafness is due to a genetic cause. Not all the genes related to hearing loss have yet been identified and only one (called Connexin 26) can be easily tested in the genetics clinic. In about 30% of children with a genetic hearing loss, the hearing loss is part of a more complicated picture, often called a ‘syndrome’. A syndrome is simply a medical term meaning a collection of signs or symptoms that doctors recognise as being linked or having the same cause.  Again, some of these syndromes can be confirmed with a genetic test, but many cannot.

Identifying a syndromic cause of deafness is helpful because it gives information about any related problems that could be checked for in the future.

Some children have a rare genetic hearing loss that can progress if they are given certain medications. It is possible to have a genetic test to identify whether they have this gene. If they do, the information helps inform the family and their doctor if, in the future, the child needs treatment.

The NDCS believes that when genetic testing is considered to be appropriate1 and is likely to provide beneficial knowledge to either the child or family, and they wish it to be done, that they are offered genetic testing. If asked for advice, the Society will ensure that the family receives accurate and unbiased information about what genetics testing can offer to enable them to make an informed choice.

Genetic screening of individuals is used to determine whether they carry a gene for a particular disease or condition that may affect them in the future or may be passed on to their children. The NDCS does not support whole-population screening for genetic conditions, with the consequent risk of moving towards a society in which difference is no longer accepted or tolerated. The NDCS does not consider that the eventual elimination of deafness, however unlikely, would be in the best interests of society.

Families with a history of deafness may choose to have prenatal genetic screening. This type of testing may identify whether the foetus has a deafness gene but is unable to predict exactly the level of deafness that the child will have. The NDCS acknowledges that some parents, whether deaf or hearing, choose to undergo this type of testing in order to prepare for the child’s future, while others may consider a termination of the pregnancy.  It is not the role of the Society to express an opinion about the way in which an individual chooses to use the information, but one of the fundamental messages that the Society will continue to broadcast is that, if the right support is provided and positive attitudes are fostered, the challenge of deafness can be a rewarding experience for deaf children and their families.

Preimplantation genetic diagnosis is in the very early stages of development. Using in-vitro fertilization (IVF) techniques, embryos are removed and selected to choose those that do or do not have a particular gene before being replaced in the uterus. It is available for couples who are at risk of passing on a limited range of genetic conditions2. This is currently not available for deafness but the NDCS acknowledges that in the future this situation might change and some families with a history of deafness may wish to use this type of technology in planning their family.

The Society views as desirable any form of research into gene-based therapy that might allow parents the choice of reducing the impact of deafness on their deaf child’s social and educational development. This type of therapy is not available currently and is unlikely to be for many years.  We do recognise that, if any form of gene-based therapy for deafness does become available in the future, the resulting improvement of hearing could possibly be more permanent than that afforded by cochlear implants or hearing aids. If this were to occur, it would pose different ethical dimensions to the choices involved; for most parents this will make the decision to use such an intervention method more complex.

The NDCS welcomes all medical discoveries which contribute to our greater and more positive understanding of deafness, empower individuals by giving them choices and enhance the potential of families to live lives which are as rich and varied as possible.

There are many factors that may result in deafness and only about half of the causes of deafness can be attributed to genetic factors. The Society welcomes the rapid advances in our understanding of the genetics of deafness, but stresses that the wider implications of all genetic research should be treated with the utmost sensitivity and care.

The NDCS recognises the rights of families with deaf children and potential parents from families who have a history of deafness to take advantage of the various genetic technologies and to use the results of such tests in a way that suits the individual family. If asked for advice, the Society will ensure that the family receives balanced and clear information about deafness in order to enable them to make an informed choice.

The NDCS will continue to campaign for a society in which deafness is not stigmatised and deaf children are viewed as individuals who have all the opportunities that are available to hearing people to develop and maximise their skills and abilities.

1. Guidelines for Aetiological Investigation; British Association of Audiological Physicians (BAAP) and British Association of Community Doctors in Audiology (BACDA), available from www.nhsp.info

2.Making Babies: reproductive decisions and genetic technologies, Human Genetics Commission, January 2006

Further information for families is available in the Health section of the website.

Or else contact our Freephone Helpline.

In addition to the policy information above, NDCS has issued this statement concerning new treatments for deafness based on genetics.