Is Amyotrophic Lateral Sclerosis (ALS) Genetic?

Medically Reviewed By Nancy Hammond, M.D.
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Amyotrophic lateral sclerosis (ALS) may be genetic. A child can inherit it from their parents. However, some people can develop the condition with no family history of ALS. This article discusses the genetics of amyotrophic lateral sclerosis (ALS). It also explains testing used to diagnose ALS, as well as the causes and risk factors of the condition.  

Is ALS genetic?

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Around 90-95% of ALS cases are sporadic, meaning that a person develops the condition without inheriting it from their family. 

Familial ALS accounts for around 5-10% of ALS cases. This is when people inherit the disease from a parent. For this type of ALS, if one parent has the disease-causing gene, they have a 50% chance of passing it to their child. 

If you have familial ALS, you may experience symptoms earlier than those with sporadic ALS. These may include muscle cramps, weakness, and slurred speech

Relatives may also have frontotemporal dementia, which is an uncommon form of dementia that damages the frontal and temporal lobe neurons of the brain. It causes overeating, problems with planning, and avoiding personal hygiene practices. This form of dementia may also have a genetic link to the development of ALS.

Read more about ALS.

ALS genetic mutation

Gene mutations occur when there is an error in the DNA instructions that cause the cell to produce high or low amounts of protein. These can also result in a defective protein. 

The National Institute of Neurological Disorders and Stroke (NINDS) states that there are more than 12 genes that can cause familial ALS. 

Some of these genes include:

  • C9ORF72: Defects in the C9ORF72 gene are the most common genetic causes of ALS, and they make up 25-40% of familial cases. People with frontotemporal dementia may also have this gene defect. 
  • SOD1: The SOD1 mutation was first identified in 1993 and was the first gene that researchers considered to be the cause of ALS. It is responsible for 12-20% of inherited ALS cases. It also helps produce the copper-zinc superoxide dismutase 1 enzyme that causes chemical reactions.
  • SPTLC1: According to a 2022 study, researchers discovered the SPTLC1 gene that causes ALS in children.
  • NEK1: It was identified in 2016 and accounts for both sporadic and inherited ALS. A 2020 study reports that hand weakness is the first symptom that you may develop if you have the NEK1 gene. 

ALS genetic testing

Genetic testing can diagnose inherited conditions and detect any gene changes that can cause health problems. 

If you have ALS and the test results show that you carry a disease-causing variant, your family members may also undergo testing to determine whether they have the same variant.

Predictive genetic testing is also available for some people who do not have any ALS-related symptoms. It requires undergoing different tests, such as a neurological and physiological exam and genetic counseling.   

A genetic counselor can also discuss the likelihood of passing on the condition to your children.  

Read about how ALS is diagnosed.

Causes of ALS

The exact cause of ALS is still unknown. However, the following factors may increase your chance of developing the condition: 

  • Genetics: Genetic mutations are the cause of inherited or familial ALS. Around 30-40% of these types of ALS cases in the United States and Europe arise as a result of the C9ORF72 gene mutations. 
  • Smoking: A 2011 study found that people who smoke may have a higher chance of developing ALS than those who do not smoke. Another study found that smoking can lead to a poorer outcome in those with ALS. 
  • Environmental toxin exposure: It is believed that people who come into contact with heavy metals, such as lead, mercury, and manganese, may have an increased chance of developing ALS. 

Read more about the causes of ALS.

ALS risk factors

Some factors may increase your risk of developing ALS more than others. These risk factors include:

  • Age: The condition can affect individuals of any age, but it seems to be more common in people ages 55 years and older. 
  • Gender: The condition affects more people assigned male at birth than those assigned female at birth. However, this difference disappears as individuals age.  

Frequently asked questions

Nancy Hammond, M.D., has reviewed these questions frequently asked about ALS.

What age does ALS usually start?

ALS can appear at any age, but it mostly affects people between the ages of 55-75. It is also more common in people assigned male at birth than those assigned female at birth. 

Over time, it affects individuals equally. 

What is the main cause of ALS?

Researchers do not yet know exactly what causes ALS. However, inherited cases can occur if one of your parents carries a gene that can increase your risk of getting ALS. 

Environmental factors may also cause ALS, and these include smoking and toxin exposure.


ALS is a rare disease that reduces the nerve cells’ function that controls voluntary movements, such as walking, chewing, and talking. 

It can affect people of any age, but most receive a diagnosis between the ages of 55-75. 

Most ALS cases are sporadic. This means that they occur in people who do not have a family history of the disease. Researchers estimate that only 5-10% of cases are inherited. 

If you have ALS, you may undergo genetic testing. This can determine the cause of your symptoms and help to determine the chances of your children inheriting the condition.

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Medical Reviewer: Nancy Hammond, M.D.
Last Review Date: 2023 Jan 31
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