Hereditary testing for ALS can help determine your risk for the condition, aid treatment decisions, and provide insight into your outlook.

Amyotrophic lateral sclerosis (ALS) is a neurological disorder that causes loss of muscle control. It’s not entirely clear what causes ALS, but most cases are sporadic, meaning that they occur during your lifetime rather than being inherited.

However, up to 10% of ALS cases may have a genetic component. While it’s not common for ALS to run in families, genetic testing may help you understand your risk if you have a family history.

This type of testing may also help a doctor make treatment recommendations if you already have ALS. One of the medications doctors use to treat ALS is intended for use in people with a specific ALS-causing genetic mutation.

If you’re considering genetic testing for ALS, talk with a doctor about the following information on what you can expect, including the risks versus benefits.

In many cases, doctors can use ALS genetic testing as a diagnostic tool to confirm the condition and help influence treatment decisions.

Hereditary ALS is also known as familial or genetic ALS. Not everyone who has a family member with ALS will develop ALS. In fact, the overall risk is low.

However, you may be able to undergo testing for the more than 12 inherited known gene mutations with links to familial ALS.

Specifically, experts think that between 25% and 40% of familial ALS is attributed to C9orf72 gene mutations. SOD1 gene mutations make up between another 12% and 20%.

Hereditary testing for ALS isn’t necessary for a diagnosis, though a doctor might recommend it if a family or close relative has this neurological disorder.

One benefit of ALS hereditary testing is that it provides information about the presence of genetic mutations that could possibly increase your risk of developing the condition. Overall, this is the most common reason why people undergo ALS genetic testing.

It’s important to know that the presence of ALS genetic mutations is a risk factor for the disease and doesn’t mean you will definitively develop this condition.

Instead, being aware of this increased risk can help you and your loved ones know when to contact a doctor in the future if you start experiencing possible early signs and symptoms of ALS.

While there’s currently no cure for ALS, early treatment may help decrease disease progression and also improve your overall quality of life.

If you already have an ALS diagnosis, genetic testing may help you and your doctor understand more about your disease and even provide insight into its future course. Different genetic subtypes of ALS tend to have different features. For example, C9orf72 and FUS mutations may be more likely to present with frontotemporal dementia than SOD1 mutations.

Another benefit of genetic testing for ALS is to help a doctor determine the best treatment options for your condition. This is especially the case for tofersen (Qalsody), a type of targeted therapy Food and Drug Administration (FDA)-approved in 2023 for treating ALS in people with SOD1 gene mutations.

There are no known physical risks associated with ALS genetic testing. However, there are certain psychological and social risks to discuss with a doctor ahead of time, as learning about ALS genetic mutations can cause emotional distress, depression, and anxiety and may strain relationships.

Another important consideration is cost. Most insurance companies will not cover hereditary testing unless a doctor specifically orders it. If they do cover it, they may only cover it partially. Therefore, it’s important to talk with both your doctor and insurance company about the expected out-of-pocket costs before undergoing testing.

Before undergoing ALS hereditary testing, you will meet with a genetic counselor. They’ll review the test details with you and help you understand the results when they come back from the laboratory.

Genetic counselors can also address psychological and social risks versus benefits before ordering tests. They can help you determine whether the benefits of obtaining this information outweigh any potential negative impacts from a social and psychological standpoint.

The procedure for genetic testing for ALS is similar to other types of hereditary tests. Depending on the facility, healthcare professionals may take a saliva, blood, or tissue sample. They then send the sample to a lab where it undergoes analysis for the presence of ALS genetic mutations.

ALS hereditary testing may take place in a hospital, office setting, or at home. Depending on the lab, you may get the results in as little as a few weeks, though sometimes it can take up to a few months.

What are the odds of inheriting ALS if one of my parents had it?

About 10% of people with ALS have inherited genetic mutations that cause the disease. The exact chances of developing ALS from a parent depend on the specific mutation.

The most common inherited mutation, C9orf72, has an autosomal dominant inheritance pattern, meaning you have a 50% chance of inheriting it from a parent. It also has a high penetrance, meaning if you have the gene, you’ll likely develop the condition.

But the various genes responsible for ALS differ in their inheritance patterns and penetrance.

If one of my family members has an ALS gene mutation, should I be tested?

Most people who have a family member with ALS do not go on to develop ALS themselves. However, development and onset can depend on several factors, including the gene affected and other ALS risk factors.

Genetic testing for ALS might provide clarity as to whether you carry one of the genetic mutations linked to familial ALS. However, it would not be definitive in predicting whether you would develop the disease or not.

At what age does familial ALS start?

Overall, there is no set timeline for when familial ALS may develop. In general, ALS can develop at any age, but the onset is most common in adults ages 55 to 75 years.

Reports exist of some genetic forms of ALS starting as young as 4 years old, but this is rare.

Can ALS skip generations?

Since not everyone with ALS gene mutations will develop this condition, it’s not clear whether ALS can skip generations. Typically, if hereditary ALS runs in your family, there will be at least one person who has this condition or frontotemporal dementia.

How much does ALS hereditary testing cost?

ALS hereditary testing may cost between $1,600 and $5,000. However, certain sponsored labs may offer the test for free to certain eligible people.

Some insurance companies may cover all or part of the cost if a doctor recommends testing, but it’s important to verify this with your provider ahead of time.

Genetic testing for ALS can help provide critical information if you have this condition or if you have a family history of ALS. This is a personal choice, though, and one that you should make in consultation with a doctor.

If you have a family member with ALS and test positive for specific genetic mutations, a doctor will encourage you to report any possible signs of this condition. Early detection can help you get treatments to potentially slow disease progression.