Around 90 percent of amyotrophic lateral sclerosis (ALS) cases are considered sporadic with no family history of the disease, but the remaining 10 percent are cases where ALS runs in the family. Often patients with familial ALS (FALS) also suffer from frontotemporal dementia, which is due to mutated genes that get passed down through the family. Carriers of the mutated genes have a 50-50 chance of passing it on to their children.
If two or more members of a family have or have had ALS or frontotemporal dementia, then other members may consider undergoing genetic testing.
A genetic counselor will take a detailed medical family history. They’ll evaluate the risk of a person developing the disease and discuss the impact of the condition. A person does not have to go through with genetic testing if they don’t want to or if they feel their risk is fairly low. There are many reasons why a person might decide not to be tested for the disease and your counselor will discuss the pros and cons of testing.
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We’ve put together a list of facts about genetic testing for FALS using information from the ALS Association:
- Genetic testing can help determine the cause of a person’s ALS, so is most useful once a person has been diagnosed to establish if the ALS is sporadic or familial.
- People with a history of the disease in their family will have a 60 percent to 70 percent chance of testing positive for one of the known mutated genes.
- Not all people with FALS will test positive, some may have the disease due to mutations which have yet to be discovered.
- If a mutation is discovered, family members may wish to undergo predictive testing to see if they also have the gene. If they do, it does not mean that they will necessarily develop ALS. Medical centers often require patients to undergo neurological and psychological tests and counseling before being tested.
- The test is done either by a blood test or a saliva sample. Results can take anywhere from a few weeks to a few months depending on the types of tests ordered by the doctor.
- FALS is a disease that presents in adulthood, so it’s not recommended for family members under the age of 18 to be tested.
- Due to the complicated nature of the genes involved, interpreting results may be difficult in some cases.
- Some people may choose not to find out if they are more at risk of the disease, whereas others may want to know so they can make informed choices about parenthood and other major life decisions.
- Genetic testing will only determine if you have one of the discovered mutated genes associated with the disease. It will not diagnose the disease if there are no symptoms and it will not predict when or if you’ll develop the disease.
- Genetic testing can be expensive and may not be covered by your health insurance. Checking for a known gene can cost around $400, whereas checking for all the known FALS gene mutations can cost between $1,600 and $5,000.
ALS News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or another qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.