Genetics and deafness

1.  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 lead lives which are as rich and varied as possible.

2.  NDCS views as desirable 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 to 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 and deaf young people this will make the decision to use such an intervention method more complex.

3. There are many factors that may result in deafness and only about half of the causes of deafness can be attributed to genetic factors. NDCS 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.

Genetic Counselling and Testing

4.  Genetic testing and counselling services should be offered to deaf children and young people and their parents where it is wanted and considered to be appropriate in providing beneficial knowledge to either the child or family.

5.  NDCS urges the development of services that are fully accessible to deaf parents and young people who have BSL as their first language.

6.  NDCS urges the development of research and services that:

a)  enable the early identification of disabilities that may, at some point in a deaf person’s life, co-exist with deafness so that appropriate intervention plans and services can be put in place

b)  identify the vulnerability of the child to medication that if administered will create hearing loss or exacerbate the degree of hearing loss.

Genetic Screening

7.  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.

8.  NDCS acknowledges that some parents, whether deaf or hearing, choose to undergo prenatal genetic 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 NDCS to express an opinion about the way in which an individual chooses to use the information, but fundamental messages that NDCS will continue to promote include:

a)  Deaf children and people make a positive contribution to society and can have happy and rewarding lives

b)  If appropriate support is provided to the family and child and positive attitudes are fostered, there is no reason why deaf children should not achieve at the same level as hearing children. 

9.  It is not the role of NDCS to express an opinion on the way society decides to make use of pre-implantation genetic diagnosis.

In conclusion, 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, NDCS will endeavour ensure that the family receives balanced and clear information about deafness and genetic technologies in order to enable them to make an informed choice.

NDCS will continue to campaign for a society in which childhood 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. 

Note: factual changes to this section will be made from time to time to keep up with recent developments in genetics without requiring Trustee Board approval unless they require changes to policy. 

1.  Introduction

1.1  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’.

1.2  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.

1.3  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.

1.4  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.

NDCS vision and values

1.5  Our vision is a world without barriers for every deaf child. We believe that:

• every deaf child has the right to the same opportunities as a hearing child
• every deaf child has the right to be included and valued by society
• families have the right to make informed choices on behalf of their deaf child and for those choices to be implemented
• families have the right to clear and balanced information and support, delivered in a way that is accessible to them.

1.6  NDCS’s youth strategy also emphasises that deaf children and young people have the right to information and fully participate in decisions that affect their lives

1.7  NDCS is committed to empowering parents of deaf children, and deaf children and young people themselves, to make informed choices, by providing impartial advice and information on all aspects of childhood deafness. The field of genetics is wide and fast growing and NDCS feels it is important to clarify its position regarding different areas of genetics and genetic research.

1.8  NDCS’s attitude to genetic developments is based on:

a)  A belief that deafness should not be regarded as an illness or a life-threatening or life limiting condition. The social model of disability on which NDCS draws on its response to issues relating to genetics, asserts that deafness in itself is not a disability but the way society responds to it does disable people.

b)  NDCS policy on inclusion which states that: NDCS believes that inclusive practice arises from a philosophy which views diversity of strengths, abilities and needs as natural and desirable, bringing to any community the opportunity to respond in ways which lead to learning and growth for the whole community, and giving each and every member a valued role.

2.1  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.

2.2  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.

2.3  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. 

3.1  Families with a deaf child may be offered a genetic test. This may happen shortly after a baby has been identified as being deaf following newborn hearing screening. Alternatively, families with older children and young people themselves may be offered a test.

3.2  Genetic testing 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. Families will also be asked about any family history of deafness and this information can be a very important part of identifying a genetic cause.

3.3  It has been established that permanent hearing loss in about 50 per cent of children is due to a genetic cause. However, not all the genes related to hearing loss have yet been identified and only one (called Connexin 26) is routinely tested for in the genetics clinic. Some others can be requested specially (for susceptibility to ototoxic medications, some syndromes and so on, for example). 

3.4  An altered Connexin 26 gene affects the functioning of the hair cells within the cochlea and causes sensory-neural hearing loss. This means that the sound cannot be transmitted to the auditory nerve and onwards to the brain. Children who have a hearing loss due to Connexin 26 do not usually have any associated conditions. 

3.5   In about 30 per cent of children with a genetic hearing loss, the hearing loss is part of a more complicated picture, known as 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. Genetic testing for a syndrome is not routinely available and is usually only offered if the child has other signs or symptoms. For example, in Ushers syndrome progressive blindness is part of the syndrome in addition to the hearing loss.

3.6  Improved knowledge of genetics and improvements in genetic diagnosis could enable earlier identification of other disabilities that coexist with deafness and develop later in life (for example: visual disorders such as Usher syndrome, keratitis-ichthyosis-deafness (KID) syndrome, Alstrom syndrome; kidney dysfunctions such as in Alport syndrome; heart conditions as part of Jervell and Lange-Nielsen-syndrome). This will help families and professionals plan for educational and health care needs including audiology care. Having a certain syndrome, for example, may mean that a hearing loss will worsen over time and therefore more frequent hearing checks may be needed.

3.7  NDCS therefore supports the development of genetic diagnosis and would want the NHS to ensure such a service was widely available and accessible to deaf children, young people and their families. 

Genetic vulnerability to medicines
 
3.8  Some children have a rare genetic susceptibility to deafness as a result of the administration of certain medications, most frequently given in response to life-threatening conditions. It is possible to have a genetic test to identify whether they have this gene. If they do, the information can help inform the family and their doctor prior to the treatment.  

4.1  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. 

Prenatal Genetic Screening

4.2  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.  

5.1  Preimplantation genetic diagnosis involves using in-vitro fertilization (IVF) techniques where 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 routinely available for couples who are at risk of passing on a limited range of genetic conditions. This is currently not routinely available for deafness but NDCS acknowledges that some families with a history of deafness may wish to use this type of technology in planning their family.

5.2  Section 14 of the Human Fertilisation and Embryology Act 2008 means that where families are undergoing IVF treatment, an embryo with an ‘abnormality’ that will develop into a ‘serious physical or mental disability’ must not be deliberately selected. The Act does not require families to undergo screening for such abnormalities, but where a screening has taken place, such embryos cannot then be ‘preferred’ if other healthy embryos are available.

• Alport Syndrome
  The second most common inherited cause of kidney failure. Hearing and vision loss is associated with Alport Syndrome.
  
  
• Alstrom Syndrome
  A rare progressive genetic disorder characterised by obesity, obescity  deafness and visual problems in childhood and diabetes and kidney failure in adults.
  
  
• Keratitis-ichthyosis-deafness syndrome
  An inherited disorder in which affected persons have:
  (i) Keratitis – gradual destruction of the cornea of the eye sometimes leading to blindness.
  (ii) Ichthyosis – localised areas of disfiguring reddish thickened skin.
  (iii) Deafness at birth.
  
  
• Jervell and Lange-Nielsen-syndrome
  A rare syndrome that causes deafness and a disruption of the heart's normal rhythm. Beginning in childhood the irregular heartbeats increase the risk of fainting and sudden death.

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.