90 Percent of People With ALS Have This in Common, Experts Say

When probing family histories of people with ALS, researchers noticed this surprising commonality.

Amyotrophic lateral sclerosis, better known as ALS or Lou Gehrig's disease, is a rare neurological disorder that that approximately 20,000 U.S. residents are living with during any given year. And while your chances of receiving an ALS diagnosis may be relatively low, the prognosis for people with ALS is dire. According to the Centers for Disease Control and Prevention (CDC), patients with ALS typically live just two to five years after first displaying symptoms, which typically include muscle weakness or stiffness, spasms, fatigue, and difficulty swallowing, among others.

Researchers know that these symptoms arise due to the disease attacking motor neurons in the brain and spinal cord which are needed for muscle movement, but the root cause of ALS is still unfortunately unknown. Experts say that both genetic and environmental factors likely play a role. In fact, there's one genetic factor that may give you an insight into your risk level. Read on to discover the one thing 90 percent of people with ALS have have in common.

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Ninety percent of ALS patients have "sporadic ALS."

ALS patient and therapy

According to the ALS Association (ALSA), roughly 90 percent of patients have "sporadic ALS," a type of ALS that is not inherited through genetic mutations. In these cases, the person diagnosed is the only person in their family with the disease. The onset of their disease typically occurs later than it does in patients with a known family history of ALS.

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The other 10 percent of patients have "familial ALS."

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The remaining 10 percent of ALS cases are considered "familial ALS" (FALS). "In these cases, more than one person in the family has ALS and sometimes family members have frontotemporal dementia as well. People with FALS often start showing symptoms at earlier ages than in sporadic ALS," writes Deborah Hartzfeld, MS, a certified genetic counselor (via the ALSA).

This statistic can spur confusion for some about one's odds of developing ALS depending on family history. While nine out of 10 people with ALS will have no known family history, you're much more likely to develop ALS if you've got a family history of the disease than if you do not.

Familial ALS patients have a 50 percent risk of passing the ALS gene on to their children.

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The FALS gene mutation is most often autosomal dominant, meaning only one parent must have it in order to pass it onto their children. It also means that the affected parent has one copy of the gene with a mutation and one without, meaning they have a 50 percent chance of passing it the mutation on to their offspring.

According to the ALS Association, "typically, although not always, there will be someone in each generation with ALS and/or dementia," which appears alongside ALS in one third of cases. It is worth noting that not everyone with the genetic mutation will go on to develop symptoms of ALS.

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Genetic testing may help you get answers.

A confident male doctor sits across from an unrecognizable female patient and holds a medication. He gestures as he explains the new prescription.

Though 90 percent of ALS cases are not the result of an inherited genetic mutation, genetic screening can help you better understand your risk if you do have a family history. This will typically require either a blood or saliva test, and can take several months to get results. The results can only be interpreted if the person in your family diagnosed with ALS is also able to participate in testing.

However, the ALSA points out that even with genetic testing, you cannot rule out the possibility of passing on familial ALS. "Not having an identified genetic mutation does not eliminate a FALS diagnosis and other family members may still be at risk for developing ALS," the organization explains. Speaking with your doctor is the first and most important step to find out your personal risk—especially if you're presenting with any possible ALS symptoms.

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Lauren Gray
Lauren Gray is a New York-based writer, editor, and consultant. Read more
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