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ALS (amyotrophic lateral sclerosis) is a progressive neurodegenerative disease that attacks motor neurons, weakens voluntary muscles throughout the body, and leads to paralysis.
For most people diagnosed with ALS, the cause of their disease is unknown. Sometimes, however, a genetic cause can be identified that explains why a person developed ALS. When a person has no family history of ALS, frontotemporal dementia (FTD), or related conditions, a genetic cause can be found about 10% of the time. When there is a clear family history of ALS, FTD, or related conditions, a genetic cause can be found about 70% of the time. |
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Genetic testing for ALS has become more accessible and more affordable in recent years. It can provide helpful information both for people who already have ALS and for family members who want to know whether they might develop ALS in the future.
What is genetic ALS?
Our DNA provides instructions for how our body will grow and function over time. We all have many differences, or variants, in our DNA, and most of them don’t impact our health. However, sometimes there can be a difference in the DNA code that can cause a problem in the body. This is called a pathogenic variant, which may also be referred to as a mutation.
Some genetic variants can cause a person to develop or be at risk of developing a disease like ALS. Researchers have now identified variants in over 40 genes that either cause ALS or increase a person’s likelihood of developing ALS. Some of the most common genetic causes of ALS are variants in the genes C9orf72 (C9) and SOD1.
Some genetic variants can cause a person to develop or be at risk of developing a disease like ALS. Researchers have now identified variants in over 40 genes that either cause ALS or increase a person’s likelihood of developing ALS. Some of the most common genetic causes of ALS are variants in the genes C9orf72 (C9) and SOD1.
Frontotemporal Dementia (FTD) and ALS
In some cases, there is a genetic association with ALS and frontotemporal dementia (FTD), a brain disorder that can cause changes in personality, behavior, and language. There are multiple genes that can cause ALS and FTD in the same person or in the same family. The most common ALS-associated gene, C9orf72, is also the most common genetic cause of FTD. Family members with C9 may develop ALS, FTD, or both. Learn more about FTD
Who could have genetic ALS?
When a person already diagnosed with ALS has a positive test result (a genetic cause is found for their ALS), it has implications for their family members. For most genetic forms of ALS, this would mean that children and siblings have a 50% chance of inheriting the same variant.
If a person with ALS has no family history of ALS and negative (normal) comprehensive ALS genetic testing, their family members are likely to have the same level of risk as the general population.
If a person without symptoms tests positive for a genetic variant, it does not necessarily mean that person will develop ALS. Different genetic variants have different levels of penetrance, which means that some variants are associated with a higher likelihood of causing ALS, and some have a lower likelihood.
A genetic counselor or other clinician with genetics expertise can help you better understand what any variant identified in your family could mean for you. Our knowledge is advancing, and we know more about penetrance for some variants than for others.
The best way to determine your likelihood of developing ALS is to discuss your family history with a genetic counselor and to consider genetic testing.
If a person with ALS has no family history of ALS and negative (normal) comprehensive ALS genetic testing, their family members are likely to have the same level of risk as the general population.
If a person without symptoms tests positive for a genetic variant, it does not necessarily mean that person will develop ALS. Different genetic variants have different levels of penetrance, which means that some variants are associated with a higher likelihood of causing ALS, and some have a lower likelihood.
A genetic counselor or other clinician with genetics expertise can help you better understand what any variant identified in your family could mean for you. Our knowledge is advancing, and we know more about penetrance for some variants than for others.
The best way to determine your likelihood of developing ALS is to discuss your family history with a genetic counselor and to consider genetic testing.
How can genetic counseling be helpful?
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The thought that you and your family members could have a genetic form of ALS can be frightening and overwhelming. Because understanding genetic risk for ALS is complicated, and because every family situation is unique, it can be very helpful to meet with a genetic counselor.
Genetic counselors are healthcare professionals who are trained in both genetics and counseling. They can discuss your family history and experience with ALS/FTD, the potential impact of learning that the cause may be genetic, and more. Genetic counselors can help guide and support you from the very beginning of the process of thinking about whether testing is right for you. |
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You can always speak with a genetic counselor to learn more and then decide that you don’t want to test.
Genetic counseling is strongly recommended for asymptomatic people with a family history of ALS who are considering genetic testing.
A genetic counselor can:
A genetic counselor can:
- Answer your questions
- Share information that can help you make the testing decision
- Decide which type of testing is most appropriate for you
- Facilitate the testing process
- Interpret and explain the results
- Provide emotional support
- Help you communicate results with family members
- Recommend any relevant treatments and clinical trials to discuss further with your doctor
- Discuss financial, career, and family planning implications as needed
- Connect you to additional resources
Access to genetic counselors can vary widely depending on where you live. Generally speaking, there are not enough qualified genetic counselors to meet demand. Ideally, you will find a genetic counselor who specializes in ALS. If not, any board-certified genetic counselor should be qualified to guide you through the testing decision and testing process.
You can ask your neurologist, doctor, or testing program to connect you with a genetic counselor. Depending on current research studies, you may be able to access a genetic counselor through a research program as well.
You can ask your neurologist, doctor, or testing program to connect you with a genetic counselor. Depending on current research studies, you may be able to access a genetic counselor through a research program as well.
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Get no-cost access to a genetic counselorLight The Way is an online platform for those who have a diagnosis of ALS, family history of ALS, or symptoms of ALS. Light The Way can offer you a cost-free genetic test should you decide to have one, pre- and post-test genetic counseling, and educational materials. Learn more
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Who should get tested?
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If you have already been diagnosed with ALS, you may choose to get tested to find out if a genetic cause can be found for why you developed ALS. This is called diagnostic testing. Current guidelines state that anyone who has ALS should be offered genetic testing for at least the most common genetic variants. Deciding whether or not to get tested is a highly individual decision.
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If you are exhibiting ALS-like symptoms but have not been diagnosed, you may also choose to get tested.
If you do not have symptoms, but have a family history of ALS (more than one relative who has been diagnosed or a family member who tested positive for a variant linked to ALS), you can choose to test to find out if you have a genetic variant linked to ALS. This is called predictive testing. This is a very personal decision that can have major life implications and should only be completed with a genetic counselor after genetic counseling.
Because of the recent identification of many more genes associated with ALS, people who tested negative years ago may want to ask their provider if it makes sense to test again.
If you do not have symptoms, but have a family history of ALS (more than one relative who has been diagnosed or a family member who tested positive for a variant linked to ALS), you can choose to test to find out if you have a genetic variant linked to ALS. This is called predictive testing. This is a very personal decision that can have major life implications and should only be completed with a genetic counselor after genetic counseling.
Because of the recent identification of many more genes associated with ALS, people who tested negative years ago may want to ask their provider if it makes sense to test again.
Testing considerations for people living with ALS
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People already living with ALS may choose to get tested for various reasons. In addition to understanding the cause of the disease, learning you have a specific variant may help you access a targeted drug, enroll in a targeted clinical trial, anticipate future care needs, and make informed family planning decisions.
If you test positive for a variant in SOD1 and live in the United States, you can discuss the option of accessing tofersen (Qalsody) with your doctor. Tofersen is a gene-targeted drug that has been shown to slow disease progression. |
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Some people living with ALS get genetic testing because they want to help their children, grandchildren, siblings, and extended family understand their potential risks. If a person with ALS tests positive, family members could consider undergoing predictive genetic counseling and testing to find out if they also have the same genetic variant.
Keep in mind that some family members may have strong opinions about not wanting to know about a genetic risk in the family. It is important to discuss testing ahead of time and ideally strategize with a genetic counselor on how you could best communicate and share test results with your family.
Keep in mind that some family members may have strong opinions about not wanting to know about a genetic risk in the family. It is important to discuss testing ahead of time and ideally strategize with a genetic counselor on how you could best communicate and share test results with your family.
Testing considerations for people who are at risk
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Some people with a family history of ALS choose to get tested because they don’t want to live with the uncertainty and want to be able to make informed decisions about finances, career, lifestyle, and reproductive planning. Reproductive planning can be a motivation for testing because there are alternative reproductive methods that can help avoid passing down genetic risk while still having a biologically related child. Some people who learn they are at risk for developing ALS decide that they don’t want to be a parent. These are considerations that can be discussed with a genetic counselor.
Some people with a family history of ALS choose not to test for a variety of reasons, such as wanting to live life without the emotional and psychological burden of knowing they might develop ALS one day. Without medical interventions available prior to symptom development, some feel that it is not worth knowing. Others are concerned about the risk that testing positive could result in genetic discrimination in one form or another. |
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Genetic Discrimination
If a person is found to have genetic risk for ALS, there is a chance they could be discriminated against. The Genetic Information Nondiscrimination Act of 2008 (GINA) protects people in the U.S. from some but not all forms of genetic discrimination.
This law prohibits most employers and other entities from requesting or requiring genetic information from individuals or their family members. Health insurance companies and most employers cannot discriminate against people who have tested positive, but life insurance, disability insurance, and long-term care insurance companies can decline services based on genetic status. The U.S. military and employers with fewer than 15 employees are not covered under the law, which means they could discriminate against service members and employees due to their genetic status.
This law prohibits most employers and other entities from requesting or requiring genetic information from individuals or their family members. Health insurance companies and most employers cannot discriminate against people who have tested positive, but life insurance, disability insurance, and long-term care insurance companies can decline services based on genetic status. The U.S. military and employers with fewer than 15 employees are not covered under the law, which means they could discriminate against service members and employees due to their genetic status.
How does testing work?
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If you are interested in genetic testing, you should discuss your testing options with a genetic counselor or clinician who has expertise in genetics. If you decide to test, you will need to provide a DNA sample (blood, cheek swab, or saliva) that will be sent to a lab for analysis.
Turnaround time varies depending on factors such as where you live, the scope of your tests, and which testing program or lab you use. Test results in the U.S. can take anywhere from a couple of weeks to a few months. |
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What do the results mean?
There are three potential test results for genetic ALS:
If you have ALS and test positive, the cause of your ALS is most likely genetic, which means that biological family members most likely have a heightened risk of developing ALS.
If you do not have any symptoms of ALS and test positive, you are considered to have an increased chance of developing ALS. It is important to understand that testing positive does not mean that you will definitely develop ALS. Different variants have different levels of penetrance, meaning that some have a higher likelihood of causing ALS, and some have a lower likelihood.
If you do not have any symptoms of ALS and test negative, it does not mean that you will never develop ALS. It means that, based on available tests and scientific knowledge, you likely have a risk similar to that of the general population. Researchers have identified about 70% of the variants linked to ALS and believe that more will be identified in the coming years.
How helpful genetic test results are will depend on your particular situation, which is why it is helpful to work with a genetic counselor who can explain what the results mean for you.
- Positive - A suspected variant associated with ALS was found
- Negative - No known variant associated with ALS was found
- Uncertain - A variant of unknown significance was found in an ALS-associated gene, meaning that it is not currently known if the DNA abnormality might be a potential cause of ALS
If you have ALS and test positive, the cause of your ALS is most likely genetic, which means that biological family members most likely have a heightened risk of developing ALS.
If you do not have any symptoms of ALS and test positive, you are considered to have an increased chance of developing ALS. It is important to understand that testing positive does not mean that you will definitely develop ALS. Different variants have different levels of penetrance, meaning that some have a higher likelihood of causing ALS, and some have a lower likelihood.
If you do not have any symptoms of ALS and test negative, it does not mean that you will never develop ALS. It means that, based on available tests and scientific knowledge, you likely have a risk similar to that of the general population. Researchers have identified about 70% of the variants linked to ALS and believe that more will be identified in the coming years.
How helpful genetic test results are will depend on your particular situation, which is why it is helpful to work with a genetic counselor who can explain what the results mean for you.
The results of genetic testing do not determine whether or not a person has ALS. That is determined through a separate diagnosis process that involves meeting with a neurologist and undergoing a series of in-person neurological exams.
How much do testing and counseling cost?
The cost of genetic testing for ALS can vary depending on your insurance coverage, what country you live in, and the breadth of the genetic testing. Cost in the U.S. has dropped significantly in recent years.
Health insurance may cover some or all of the costs, especially when a doctor or medical professional orders your test. There may also be sponsored programs or research studies that cover all of the costs. Consult with your doctor or genetic counselor to find the best testing option for you.
Genetic counseling is included as a free service with some sponsored testing and research programs. If not, genetic counseling in the U.S. is billed just like any other visit with a healthcare professional. Check your insurance plan’s coverage for genetic counseling.
Health insurance may cover some or all of the costs, especially when a doctor or medical professional orders your test. There may also be sponsored programs or research studies that cover all of the costs. Consult with your doctor or genetic counselor to find the best testing option for you.
Genetic counseling is included as a free service with some sponsored testing and research programs. If not, genetic counseling in the U.S. is billed just like any other visit with a healthcare professional. Check your insurance plan’s coverage for genetic counseling.
Where can I get tested?
Access to genetic testing for ALS varies greatly within the US and across the world.
If you have already been diagnosed with ALS, your neurologist may or may not offer you genetic testing. If you are interested, tell your neurologist that you would like to learn more and know what your options are. Your neurologist, genetic counselor, or even a primary care doctor comfortable with genetics can order the test for you.
If you don’t have symptoms and have a family history of ALS, a genetic counselor can facilitate your testing process.
Here are some no-cost testing options for people who have been diagnosed with ALS or have a family history of ALS:
If you have already been diagnosed with ALS, your neurologist may or may not offer you genetic testing. If you are interested, tell your neurologist that you would like to learn more and know what your options are. Your neurologist, genetic counselor, or even a primary care doctor comfortable with genetics can order the test for you.
If you don’t have symptoms and have a family history of ALS, a genetic counselor can facilitate your testing process.
Here are some no-cost testing options for people who have been diagnosed with ALS or have a family history of ALS:
- ALS Identified is a no-charge genetic testing program that is sponsored by Biogen, offered through Invitae, and available for people 18 and older living in the U.S. and Puerto Rico. Only a healthcare professional like your doctor can order the test for you.
- Light The Way is an online platform that offers no-cost at-home genetic counseling, testing, and education. It offers mail-in-only genetic testing, so you don’t need to visit a doctor to participate. It is a research study, so test results may not appear on your medical record.
- Prevention Genetics provides no-cost ALS genetic testing, sponsored by Ionis, for residents of the U.S. and Canada. The test must be ordered by a qualified healthcare provider. Participants can receive one free counseling session before testing and another after testing
If you get tested through your doctor or another healthcare professional in a clinical setting, your results will become part of your medical record. If you get tested through a research study, your results may not become part of your medical record, depending on the protocol. If you are concerned about potential genetic discrimination, ask if the results will appear on your medical record before choosing a testing pathway.
Recreational genetic tests such as AncestryDNA and 23andMe should not be used for ALS genetic testing, even if results appear to provide helpful information related to ALS. These tests don’t use the correct testing, processing, or results return process to manage complex information like genetic ALS/FTD testing. They could provide false reassurance.
Learn more
Genetic ALS is a complex topic with many nuances and highly variable individual circumstances. The best thing you can do is meet with an ALS genetic counselor, neurologist, or other healthcare professional who can answer your specific questions.
Here are some helpful online resources where you can find additional information, guidance, and support:
Here are some helpful online resources where you can find additional information, guidance, and support:
- The Find a Genetic Counselor Tool can help you find a genetic counselor for virtual or in-person visits if you live in the U.S. or Canada.
- The My ALS Decision Tool™ by Les Turner can walk you through the genetic testing process and help you make informed decisions.
- End the Legacy is an advocacy organization and community that provides support and education to people impacted by genetic ALS and FTD.
- The ALS Association takes a deeper dive into genetic mutations, risk, inheritance, testing, and more.
- The ALS Canada Gene Hub provides detailed information on ALS genetics, testing, opportunities, and resources.
- The Association for Frontotemporal Degeneration provides education and support for families impacted by FTD.
- You can watch the Penn FTD Center’s current and past Annual Familial Conferences to learn more about familial ALS/FTD.
- Ginahelp.org is an online resource that summarizes and answers common questions about the Genetic Information Nondiscrimination Act in the U.S.
In Summary...
- The majority of people diagnosed with ALS do not have a genetic form of ALS.
- Genetic ALS is more likely when there is a family history of ALS and/or FTD.
- Genetic testing can sometimes—but not always—identify whether a person has a genetic variant associated with ALS.
- When a genetic cause is found, it has implications for the person diagnosed and for family members.
- Deciding whether or not to get tested is a highly personal decision.
- Genetic counselors can provide guidance, support, and information to help people understand their situation and decide whether genetic testing is right for them.
- Genetic counseling is strongly recommended for asymptomatic people with a family history of ALS who are considering genetic testing.
- Genetic testing has become much more affordable and may even be free.
Your ALS Guide developed this page in collaboration with genetic counselor Laynie Dratch and Dr. Paul Wicks.
