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ALS vs. SMA: What's the Difference?

Edited by Aimie Carlson || By Janet White || Published on February 13, 2024
ALS (Amyotrophic Lateral Sclerosis) is a neurodegenerative disease affecting motor neurons, leading to muscle weakness; SMA (Spinal Muscular Atrophy) is a genetic disorder causing progressive muscle wasting due to motor neuron loss.

Key Differences

ALS is characterized by the degeneration of motor neurons leading to muscle weakness and atrophy. SMA is a genetic disorder caused by a deficiency in the SMN1 gene, leading to progressive muscle weakness.
The onset of ALS typically occurs in adulthood, often leading to rapid progression and severe disability. SMA usually manifests in infancy or early childhood, with varying degrees of severity depending on the type.
ALS affects both upper and lower motor neurons, resulting in a combination of muscle weakness, spasticity, and atrophy. In SMA, primarily lower motor neurons are affected, leading to muscle wasting and weakness without sensory loss.
There is no known cure for ALS, and treatments are focused on managing symptoms and prolonging survival. For SMA, recent advancements in gene therapy and treatments targeting the underlying genetic cause offer potential for significant improvement.
The progression of ALS can lead to total paralysis and respiratory failure. While SMA can also lead to severe physical disabilities, its course is more variable, and some forms are compatible with a longer lifespan.

Comparison Chart

Primary Cause

Neurodegeneration of motor neurons
Genetic deficiency in the SMN1 gene

Age of Onset

Usually in adulthood
Infancy or early childhood

Affected Neurons

Upper and lower motor neurons
Mainly lower motor neurons

Treatment and Prognosis

Symptom management, no cure
Gene therapy, varying prognosis

Typical Progression

Rapid progression to paralysis
Variable, dependent on SMA type

ALS and SMA Definitions


A neurodegenerative disease affecting motor neurons.
He was diagnosed with ALS, which affected his muscle control.


Affects motor neurons in the spinal cord.
In SMA, the motor neurons in the spinal cord degenerate.


Involves both the brain and the spinal cord.
ALS progresses by affecting neurons in the brain and spinal cord.


Results from a deficiency in the SMN1 gene.
Genetic testing revealed the SMN1 gene mutation responsible for SMA.


No known cure, treatment focuses on symptom relief.
Her treatment for ALS focused on managing symptoms and improving quality of life.


A genetic disorder causing progressive muscle weakness.
The child with SMA showed signs of muscle weakness early on.


Often leads to severe disability and paralysis.
As ALS advanced, he required more assistance for daily activities.


Has variable severity, depending on the type.
Her type of SMA was less severe, allowing greater mobility.


Characterized by muscle weakness and atrophy.
ALS led to a gradual loss of her ability to walk.


Recent treatments target the genetic cause.
He received gene therapy, a new treatment for SMA.


Obsolete form of also






Thickening of tissue in the motor tracts of the lateral columns and anterior horns of the spinal cord; results in progressive muscle atrophy that starts in the limbs


What is ALS?

A progressive neurodegenerative disease affecting motor neurons.

What is SMA?

A genetic disorder causing muscle weakness due to motor neuron loss.

How is ALS diagnosed?

Through clinical evaluation, electromyography, and ruling out other conditions.

How does SMA affect the body?

It causes progressive muscle weakness and atrophy.

Is ALS hereditary?

Most ALS cases are sporadic, but some are familial.

Can ALS be cured?

There is no cure for ALS; treatment focuses on symptom management.

What causes SMA?

A genetic mutation in the SMN1 gene.

Are there treatments for SMA?

Yes, including gene therapy and medications targeting the genetic cause.

What are the symptoms of ALS?

Muscle weakness, atrophy, difficulty speaking, and breathing problems.

Is SMA always inherited?

Yes, it's an autosomal recessive genetic disorder.

Can SMA be detected before birth?

Yes, through genetic testing during pregnancy.

Are there different types of SMA?

Yes, varying from Type 1 (most severe) to Type 4 (least severe).

How is ALS managed?

With medications, physical therapy, and supportive care.

Is ALS painless?

It primarily causes muscle weakness, but some patients experience pain.

Does SMA affect cognitive abilities?

No, SMA does not typically affect cognitive functions.

What is the life expectancy with ALS?

Varies, typically 3-5 years after diagnosis, but some live longer.

Can SMA improve with treatment?

Treatment can slow progression and improve symptoms, especially with early intervention.

Who is at risk for ALS?

Adults, typically between 40-70 years old, with a slight male predominance.

Can lifestyle changes help with SMA?

Physical therapy and supportive care can improve quality of life.

Do ALS symptoms progress quickly?

Typically, yes, especially in later stages.
About Author
Written by
Janet White
Janet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.
Edited by
Aimie Carlson
Aimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.

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