What is the difference between sporadic and familial ALS?

The main difference between sporadic and familial cases of amyotrophic lateral sclerosis (ALS) is whether or not there is a family history of the disease. When ALS affects more than one person in the same biological family, it's referred to as familial ALS . The term sporadic ALS, on the other hand, is used to refer to any case of ALS in which there is no known family history of the disease. Sporadic ALS accounts for the vast majority — about 90% — of ALS cases.

What age does sporadic ALS start?

Sporadic amyotrophic lateral sclerosis (ALS) can manifest at any age, but symptoms most commonly arise in middle or late adulthood. The average age at onset for sporadic ALS is 58-63. However, there have been reports of sporadic ALS cases manifesting during childhood and younger adulthood, with some cases being caused by de novo or specific new mutations in ALS-associated genes.

Can sporadic ALS be inherited?

By definition, sporadic amyotrophic lateral sclerosis (ALS) affects only one person in a biological family. As such, sporadic ALS cannot be inherited, although patients may be born with certain genetic characteristics that contribute to their disease risk. When ALS affects multiple people in the same family, it is referred to as familial ALS .

Is there a cure for sporadic ALS?

There is no cure for any form of amyotrophic lateral sclerosis (ALS). However, there are available treatments that may slow ALS disease progression and extend survival. Therapies to help manage disease symptoms like spasticity and excessive drooling also are available.

What does sporadic ALS mean?

Q: What causes sporadic ALS?

Amyotrophic lateral sclerosis (ALS) is marked by the progressive damage and death of motor neurons, the specialized nerve cells responsible for controlling movement. In sporadic ALS, it's not known exactly what causes the disease to develop, but a number of factors including genetics, environmental exposures, and lifestyle habits are all thought to affect a person's risk.

Amyotrophic lateral sclerosis (ALS) is a progressive neurological disorder in which nerve cells that control movement break down and die. ALS is also known as Lou Gehrig’s disease and can be classified as familial or sporadic ALS, depending on whether the disease runs in the family.

About 90%-95% of all ALS cases are sporadic, meaning they occur in people with no known family history of ALS. Although the causes of sporadic ALS remain incompletely understood, a complex interaction of genetics and environmental factors is thought to play a role in the development of the disease.

Sporadic ALS genetics: Is sporadic ALS hereditary?

By definition, sporadic ALS affects only one person in a given biological family. As such, sporadic ALS is not hereditary, meaning a parent does not pass the disease to biological children through genes. Nonetheless, researchers believe genes play an important role in influencing a person’s risk of developing sporadic ALS.

Why ALS may appear sporadic

ALS can appear sporadic because it occurs in people with no known family history of the condition. However, approximately 10% of people with sporadic ALS carry a variant, or mutation, in a gene associated with the disease.

These variants sometimes occur de novo, meaning they appear for the first time in the affected individual rather than being inherited from either parent. A de novo variant may develop in a sperm or egg cell prior to conception or shortly after fertilization.

What a gene variant could mean for relatives

If a person with sporadic ALS carries a variant in an ALS-linked gene, genetic testing can provide useful information about the chance of passing that variant to future generations. This depends on the specific variant found and its inheritance pattern.

If the gene variant is inherited in an autosomal dominant pattern, each child of a person with ALS has a 50% chance of inheriting the variant. Inheriting the variant may increase the child’s risk of ALS, but does not guarantee that they will develop it. Other factors can influence who develops the condition.

Siblings of a person with sporadic ALS may also have an increased risk of developing the condition, though the overall risk remains low.

Is genetic testing recommended for sporadic ALS?

Genetic testing for sporadic ALS offers the only way to determine whether a person carries a genetic variant linked to the disease. This may help explain why a person developed the disease and can help guide treatment.

What a positive result might mean

A positive test means a person carries a variant in an ALS-associated gene. Depending on the specific gene, doctors can prescribe an available gene-targeted therapy or determine if the person qualifies for a clinical trial. Test results also help family members decide whether to pursue their own genetic testing.

What a negative or uncertain result might mean

A negative ALS test means no known genetic variant linked to ALS was identified. This outcome does not completely rule out a genetic component, as not all genes linked to ALS have been identified or tested.

In some cases, testing reveals a genetic variant whose role in ALS remains unknown. This is called a variant of uncertain significance. If future research links the variant to ALS, it may be reclassified.

Benefits of genetic testing for ALS

Genetic testing for ALS offers several key benefits during the diagnostic process:

Identifies treatment options, including gene-targeted therapies
Determines eligibility for clinical trials
Guides informed decisions about family planning
Helps family members decide if they want to get tested
Reduces uncertainty and helps with planning long-term care

Risks of genetic testing for ALS

Genetic testing also carries potential risks and drawbacks. The testing process may:

trigger anxiety, depression, guilt, or other difficult emotions
create tension in families or relationships, particularly if results reveal shared genetic risk
yield unexpected or uncertain results that prove difficult to interpret
affect a person’s ability to get or afford life insurance, disability insurance, or long-term care insurance
raise concerns about data privacy and the use of personal genetic information

Questions to ask a genetic counselor

A genetic counselor is a healthcare professional with specialized training in genetic diseases. Counselors help patients understand genetic risks while weighing the downsides, risks, and benefits of genetic testing.

Patients might consider asking these questions:

Would genetic testing be helpful for me, and why?
What test do you recommend and why?
What are the potential benefits and risks of this test?
Does insurance cover this test?
What can this test tell me, and what can it not tell me?
How might the test results affect my treatment?

Sporadic vs. familial ALS: How are they different?

ALS manifests differently in every person, but the signs and symptoms of sporadic and familial ALS are generally comparable. The main difference between these types of ALS is whether the patient has a known family history.

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	Family history of ALS?	Prevalence	Known genetic variant
Sporadic ALS	No known history	90%-95% of cases	About 10% of people have a known genetic variant
Familial ALS	Yes	5%-10% of cases	About 60% of people have a known genetic variant

What causes sporadic ALS?

In ALS, nerve cells that control movement throughout the body die off, leading to muscle wasting. While scientists continue investigating the precise cause of sporadic ALS, a combination of genetic, biological, and environmental factors appears to play a role.

Genetics and biological processes

Most people with sporadic ALS do not have a direct genetic link to the disease. However, about 10% of individuals carry a variant in an ALS-associated gene, most commonly C9orf72, SOD1, FUS, or TARDBP.

Biological abnormalities like irregular neuronal signaling, mitochondrial dysfunction, and inflammation also contribute to motor neuron death, which characterizes ALS.

Environmental and lifestyle factors

Certain environmental and lifestyle factors can also influence the risk of developing ALS. These include:

Age: ALS most commonly develops between the ages of 55 and 75.
Male sex: The condition affects males slightly more often than females before age 65.
Head injury and trauma: The risk is higher in people with a history of severe head trauma.
Toxins: Exposure to toxic chemicals like pesticides and heavy metals may increase risk.
Certain viral infections: Infection with certain viruses, particularly enteroviruses, can increase risk.
Military service: Higher risk in military members may be due to head injuries or exposure to toxic substances.
Occupation: People who work in certain fields, such as manufacturing, welding, chemical operations, painting, construction, and mining, may have a higher risk.
Smoking: A habit of smoking may be a risk factor, particularly in women after menopause.

What are the symptoms of sporadic ALS?

Sporadic ALS affects everyone differently, but common symptoms include:

muscle weakness, spasticity, and wasting
trouble swallowing and speaking
difficulty breathing
constipation or other digestive issues
cognitive problems and dementia
pseudobulbar affect, characterized by uncontrolled bouts of laughing or crying
mental health challenges

ALS symptoms can begin at any age but usually appear in mid- to late adulthood. The average age of onset for sporadic ALS is 55 years old.

Sporadic ALS is a progressive disease, meaning symptoms worsen over time. Symptoms usually start in one body region and gradually spread. In limb-onset ALS, symptoms begin in the arms or legs, whereas in the less common bulbar-onset ALS, symptoms start in muscles controlling speech and swallowing.

Life expectancy varies widely among people living with sporadic ALS. Most people survive about three to five years after their diagnosis, but it’s estimated that up to 20% of people live longer than 10 years.

How is sporadic ALS treated?

While no cure currently exists for sporadic ALS or any other form of the disease, several treatments can help manage symptoms and prevent complications. Doctors can prescribe four approved medications for ALS. Additional management strategies include:

physical therapy
occupational therapy
speech-language therapy
nutritional support
psychological and social support
breathing support
clinical trials

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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 other 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.

What does sporadic ALS mean?