Genetic Information

Spinal Muscular Atrophy is a genetic muscle wasting disease. In most cases (but not all) each child inherits a faulty copy from BOTH of their parents, so each time they become pregnant they have a 1 in 4 chance of having a child affected by the disease. (if only one parent carried the gene there would be only a 1 in 2,500 chance of having an affected child)

We have found that if you are a carrier of the SMA gene (this doesn’t mean you are affected) that your siblings are more than likely to be carriers as well. So make sure that you inform your siblings and other extended family members like cousins, so that they understand about how it could affect them. They can then choose if they would like to be tested to see if they are a ‘carrier’ of the SMA gene (1 in 35 here in Australia)

Carrier  testing for Spinal Muscular Atrophy

SMA carrier screening  is a test that  can inform individuals if they carry the faulty SMA gene. Carrier screening for the SMA gene enables couples and families the choice to find out if they are carriers  of Spinal Muscular Atrophy. If you are a carrier it doesn’t mean you are effected by SMA, it just means that  if you match up with another carrier that there is a potential (1 in 4 chance) that you could possibly have a child with  SMA.  Having the test doesn’t rule you out for having children,  it will just enable you to have an informed choice as to your reproductive future.  Most screening will capture 85% of carriers, but in some cases SMA can be diagnosed with  one or none of the parents  being identified as carriers.

If you are identified as a carrier there is genetic  counselling available at most clinical genetic clinics.

You can start here at the Victorian Clinical Genetic Services 

Families can  also contact their local genetic counselling service. These are available in all major public hospitals in every state – just ask for the Genetics Department.

Usually when a child is diagnosed with SMA 1 or SMA 2 the immediate family should be referred for genetic counselling and then ‘cascade testing’ of other adult family members can be facilitated for them.

It is preferable that referral to these genetic counselling services is through a general practitioner, medical specialist or other health care professional.

Carrier testing is not always straight forward and give a clear cut ‘yes/no’ answer so for the best results to be interpreted correctly this should be done through a counsellor or genetic service.

What Happens in Genetic Counselling for SMA.

Genetic Counselling is proved by a team of health professionals working together to provide current information, guidance and support to assist in the understanding of the disease Spinal Muscular Atrophy.

Consultation: (Brief over view)

Discuss the impact and effects of SMA on the sufferer and their family.

Explain how and why SMA occurs, i.e. both partners have to be a carrier of SMA.

If both carriers there is a one in four chance of having a child with SMA.

One in thirty five people are carriers of SMA.

The implications and the need for Carrier testing for other siblings and family members.

Discuss other reproductive options to ensure that any decisions are made on an informed basis.

Discuss and provide current information regarding prenatal testing, offering counselling and support so that informed decisions can be made.

Discuss and arrange appropriate genetic testing.

Provide information regarding support groups, supply both verbal and written information about the disease, appropriate booklets and pamphlets.


Follow up:

After the initial consultation an opportunity may be provided to go over information and offer on-going support. It is common for people to think of many questions after the first genetic counselling consultation, also new questions arise as the condition develops. The follow up can be as simple as a phone call.

A letter should be provided summarising the initial consultation.