Should Family Members Get Genetic Testing for ALS?

If you have been diagnosed with ALS, the first step is for you to undergo genetic testing, not your children. If your results show a specific genetic mutation linked to ALS, your adult children and siblings can then choose whether they want to undergo predictive genetic testing. Because testing asymptomatic family members is a deeply personal and complex decision, it is highly recommended that families work with a genetic counselor to navigate the emotional, medical, and practical implications ^[1]. Predictive testing is generally only considered for adults, as ALS is primarily an adult-onset disease.

Sporadic vs. Familial ALS

Historically, ALS has been divided into two categories:

• Familial ALS (fALS): About 10% of people with ALS have a family history of the disease ^[2][3].
• Sporadic ALS: The remaining roughly 90% of cases occur in people with no known family history of ALS ^[2].

However, the line between these two types is blurring. Research has shown that a significant number of people with seemingly “sporadic” ALS actually carry genetic mutations linked to the disease ^[2][3]. Because of this, current medical guidelines increasingly recommend that all individuals diagnosed with ALS be offered genetic testing, regardless of their family history ^[4][2][5].

Why You Should Be Tested First

Testing family members without first knowing if the diagnosed patient carries a mutation is like searching for a needle in a haystack without knowing what the needle looks like.

If you (the patient) undergo genetic testing, doctors will look for known ALS-linked mutations, such as C9orf72 (the most common genetic cause) or SOD1 ^[6][7]. Finding a mutation in you has two major benefits:

1. Targeted Treatments: Gene-specific therapies have recently been developed or are currently in clinical trials. For example, there is a newly approved targeted treatment (tofersen) specifically for people with SOD1 mutations ^[2][8]. While treatments for other mutations like C9orf72 are still in the clinical trial phase and not yet approved, identifying your specific genetic subtype can determine if you are eligible to participate in these trials.
2. Information for Your Family: If a specific mutation is identified in your DNA, it provides a clear genetic marker that can then be used to test your family members, if they wish to know their status.

How the Testing Process Works for You

You can initiate this process by asking your neurologist or ALS clinic about genetic testing. The test itself is typically very simple, requiring only a standard blood draw or a saliva sample. Results usually take several weeks to return, at which point your doctor and genetic counselor will review them with you.

Considerations for Family Members

If a mutation is found in the diagnosed patient, their children and siblings often have a 50% chance of carrying the same genetic variant, depending on the specific mutation. However, deciding to get tested is a very personal choice for family members who do not have symptoms (known as predictive testing).

Here are important factors your family should consider:

• Incomplete Penetrance: Having an ALS-linked genetic mutation does not guarantee that a person will develop the disease ^[1]. Many people carry a mutation but never develop ALS in their lifetime.
• Psychological Impact: Knowing one carries a genetic risk for a serious condition can cause significant anxiety and emotional distress ^[9].
• Insurance and Practical Concerns: While some laws protect against health insurance and employment discrimination based on genetic information, predictive test results could affect your family members’ future ability to secure life, disability, or long-term care insurance.
• Clinical Trials: Some family members choose to get tested so they can participate in clinical trials testing preventative treatments for those with a known genetic risk ^[2].

The Role of a Genetic Counselor

Because of the emotional weight and complex nature of this information, genetic counseling is a critical part of the testing process ^[1]. Your ALS clinic can typically refer you to one. A genetic counselor will not pressure your family members to get tested. Instead, they will help your adult children or siblings understand their actual risk, discuss the psychological and insurance implications, and help them make an informed decision that feels right for them.