The vast majority of ALS cases (about 90%) are thought to be sporadic, meaning that the disease is not inherited.
In about 10% of cases, however, there appears to be a familial component. If someone is carrying a mutated gene that leads to amyotrophic lateral sclerosis (ALS), research suggests they have a 50-50 chance of passing it on to their children.
A number of different genes have so far been identified that may play a role in developing ALS and increase the individual’s likelihood of developing the disease.
Whilst many of the symptoms in sporadic and familial ALS are the same, the major difference is that individuals with familial ALS are more likely to develop prefrontal dementia. The condition also tends to occur earlier in life.
Better understanding of this familial component has led to an increase in genetic testing taking place. Genetic tests can help determine if someone has inherited a particular gene, but this does not necessarily mean that they will go on to develop the disease.
Here we take a closer look at what ALS genetic testing involves, whether it is the right option and how much it typically costs.
Familial ALS is generally defined as autosomal dominant. This means that someone who has the mutated gene has a 50% chance of passing it onto their offspring.
Affected individuals normally produce one gene with the mutation and one without. It simply depends on random chance which gene passed on to the child, irrespective of whether they are male or female.
If the child does not inherit the familial mutant gene, they in turn cannot then pass it onto their own children. For those who have a member of their family that has been diagnosed with ALS, there can be the option for them to be tested to see if they are also carrying the gene.
ALS genetic testing has the potential to highlight whether an individual is carrying a mutated gene associated with the development of the disease. Genetic testing, in general, has become popular over the last few years for a variety of different conditions that have a familial component.
For example, someone may have a parent who had ALS and they wish to check if they also have the gene before starting their own family. They may be concerned that certain members of your family are at risk from also developing the disease.
The test can be organized by a medical geneticist, doctor, nurse practitioner or specialist if there is a suspicion that someone might have a certain gene profile.
The first step involves sitting down with a genetic counsellor who will work through the process with the individual and discuss what it means. They will look at the medical and family history of the individual as well as talk about the pros and cons of ALS genetic testing and whether it is appropriate.
The test is very simple and involves either taking blood or collecting a saliva sample in a special tube. It’s normal to do this in the doctor’s office to avoid any cross-contamination that may lead to a false reading.
Once the sample is taken, it is processed by a specialist lab to determine the genetic makeup. This can take up to a couple of weeks. The results are relayed by the doctor, or the genetic counsellor, along with any advice and guidance that the individual should require.
It’s important to note that genetic testing which shows a gene related to ALS does not mean that the person in question has ALS or is definitely going to develop the disease. It is simply an indicator of the risk.
The research surrounding the genetic component of ALS is still evolving and is actually in its very early stages. Just because someone might not have a specific mutated gene for the disease it doesn’t mean they will not develop familial ALS. There may be other genes that have not yet been discovered which may have an influence.
ALS genetic testing is becoming more popular but it does come at a cost. If you are being tested for all the current known genes involved in ALS, you should expect to pay between $1,600 and $5,000. A single gene test, if it’s known, will cost between $500 and $1,500.