Most motor neurone disease (MND) is sporadic. This means that it does not run in families. Only 10% of MND is estimated to be inherited.
In this small number of cases, there is a family history of MND and/or frontotemporal dementia. Where this occurs, the disease is caused by a mistake in the genetic code which can be passed down, although other triggers are still necessary for the disease to emerge.
If you are concerned about the possibility of a family history of MND and what that could mean for those close to you (in terms of inheriting the genetic code), you may wish to seek genetic counselling.
Genetic counselling in New Zealand
The Genetic Health Service NZ sees people where a mutation is already identified in their family, or to assess a family that has not had any testing. Testing needs to start in a family member with a clinical diagnosis of MND or dementia, as this gives the most information for a family.
A family has to have two or more first-degree (eg parent or sibling) or second-degree (eg grandparent, aunt, uncle) relatives with MND and/or early onset dementia to qualify for an assessment. All appointments are funded for New Zealand residents who meet referral criteria. A referral can come from a GP or specialist.
Genetic testing identifies the cause in around 30% of familial MND. This means for many families the genetic cause remains unknown. When a mutation is known in a family, at-risk relatives can make an appointment for pre-symptomatic testing.
The first pre-symptomatic testing appointment with the Genetic Health Service will look at the family history, the inheritance pattern, the person’s motivation for testing, and the effects of testing on relationships. We later meet in person to review the results.
Some people stop the process after the first or second appointment as they decide they do not want to know, or want to delay knowing their result. As there is no cure for MND, many people do not wish to know their status. Others feel they need to know their result to properly plan for the future and make the most of their time.
Choosing to be tested or learn your status can be a very difficult decision, as it affects the wider family. The timing of the test can be very important. Two of most common times people seek genetic testing is before they have children, or before they have grandchildren.
The New Zealand government provides funding for family planning options such as testing during a pregnancy, or with IVF pregnancy, testing embryos known as Preimplantation Genetic Diagnosis (PGD). Both these testing options can only be done if a family’s genetic mutation is known. A separate appointment with the Genetic Health Service is required to thoroughly discuss family planning options and the PGD process. There is a substantial waitlist to access PGD at present. This will be discussed when the couple is seen by a fertility clinic.
Although sensitive to the emotional aspects of the situation, genetic counselling is not a form of psychotherapy. A genetic counsellor explains the facts as clearly as possible, and gives you accurate information on the implications for your family.
If you chose to undergo genetic testing, there may be an impact on your ability to obtain new insurance policies. You would have to declare genetic test results or family history if asked, and it may mean that you would not be covered for anything to do with MND and that your premiums become higher. This may not be an issue for you if you have insurance in place already. It may be advisable to speak to an independent financial or insurance advisor.
Genes that cause inherited MND
We know approximately 70% of the genes known to cause inherited MND. Currently, testing is only available for four of the genes that play a part in inherited MND:
- SOD1, discovered in 1993, accountable for 20% of cases of inherited MND
- TARDBP, discovered in 2008, accountable for 3-5% of cases of inherited MND
- FUS, discovered in 2009, accountable for 3-5% of cases of inherited MND
- C9ORF72, discovered in 2011, accountable for around 40% of cases of inherited MND
Other extremely rare causative genes have also been identified. These discoveries represent major breakthroughs because they can provide important clues as to how motor neurons are damaged in MND and may advance our understanding of all types of the disease
Further reading