Myasthenia Gravis vs ALS: What are the Differences?

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Myasthenia gravis (MG) and amyotrophic lateral sclerosis (ALS) present with many of the same symptoms, such as difficulty swallowing and muscle weakness. However, the two are different conditions.

While MG affects how the neurons and muscles communicate with one another, ALS damages nerve cells that control muscle movement. This article discusses the similarities and differences in symptoms, causes, and treatment for both conditions.

Symptoms

The symptoms present in MG and ALS are similar because the communication pathway between the brain and the muscles is compromised in both conditions. However, not all symptoms that develop will do so in both MG and ALS.

Symptoms that are specific to each condition include:

MG
  • Muscle weakness in the eyes

  • Eyelid drooping

  • Double or blurry vision

  • Changes in facial expression

  • Shortness of breath

ALS
  • Muscle twitches and cramps

  • Muscle atrophy, tightness, and stiffness

  • Nasally speech

  • Difficulty chewing

  • Difficulty breathing

Symptoms that are shared between the two conditions include:

  • Difficulty swallowing
  • Speech impairment
  • Muscle weakness

Causes

The causes of MG and ALS differ.

Myasthenia Gravis

MG belongs to a group of conditions known as autoimmune diseases, which develop when the immune system recognizes healthy cells as harmful pathogens and attacks them by mistake.

In people without MG, the brain and the muscles communicate via motor nerves, which send chemical messengers down the nerve so it can bind to a receptor. The binding passes along specific messages to the muscles in the body. This connection terminal is known as the neuromuscular junction.

When a person develops MG, immune proteins known as antibodies begin to block or destroy the receptors in the brain that receive a specific chemical messenger known as acetylcholine. When acetylcholine cannot bind to its receptor, the ability of the brain to communicate with the muscles becomes compromised.

It’s also thought that the thymus gland, which produces immune cells in childhood, plays a role in MG. The thymus gland is relatively large in childhood, but after puberty, it begins to shrink until most of it is replaced with fat. In people with MG, however, the thymus gland does not shrink as it should and remains large well into adulthood.

Because it is still present and producing immune cells, it’s thought that it malfunctions and relays the wrong message to the immune cells it continues to make, leading to them attacking bodily tissues instead of foreign bacteria, viruses, or other harmful substances.

ALS

ALS is a neurodegenerative disorder, and medical researchers are still trying to determine what causes it. Evidence suggests that a person’s genetics and environment may play a role.

From a genetic standpoint, it’s thought that over 20 different gene changes may lead to the development of the disorder. When genes mutate, the instructions they provide change along with them and can cause issues with how the entire system functions.

In ALS, specific genes known as C9orf72, SOD1, TARDBP, FUS, and TBK1, are thought to be the most common genetic culprits behind the disease.

Exposure to viruses, physical trauma, poor diet, and toxic or infectious agents may also lead to someone developing ALS. However, more research is needed to determine how these aspects affect the disease.

ALS and Viruses

While medical researchers are weary of assigning any virus to the cause of ALS, some recent research in animal studies has found that some may be directly associated with a higher risk of the disease. They include:

  • Polio
  • Coxsackievirus
  • Echovirus
  • Enterovirus-A71
  • Enterovirus-D68

Diagnosis

Since MG and ALS can present with the same symptoms, there is some overlap in the diagnostic process. Both conditions are examined first using a physical examination and health history collection. Other tests that may be used for both include:

That is where the similarities end when it comes to testing.

Myasthenia Gravis

MG will also be diagnosed using other tools, including an edrophonium test, which temporarily blocks the impairment or damage to acetylcholine so that levels can increase. The result allows healthcare providers to determine muscle weakness in the eyes.

While blood tests are used for both, a specific type is used for MG that looks for heightened levels of two different antibodies: acetylcholine receptor antibodies and the anti-MuSK antibody. Not everyone with the disease will have elevated levels of both, but the results can aid the diagnostic process.

To measure breathing in people with MG, pulmonary function testing will also be done to determine the strength of a person’s breath to see if they are at risk for a myasthenic crisis.

What is a Myasthenic Crisis?

The muscles in people with MG can sometimes become so weak that they cannot breathe independently. If that happens, it is referred to as a myasthenic crisis, and it is life-threatening if not addressed quickly. 

ALS

While most of the diagnostic tools used to determine a case of MG are used in ALS, one such test is only used for ALS, and that is a muscle biopsy, which is when a piece of muscle is removed and sent to a lab for closer examination.

The results will help medical providers establish that the symptoms are not occurring because of a disease that directly affects the muscles.

Treatment

Treatments for both MS and ALS vary, so getting a proper diagnosis is crucial before implementing a treatment plan.

Myasthenia Gravis

Since the cause of MG is clear, viable treatment options have been developed to significantly improve the quality of life for people with the disease. First-line therapy options for MG include:

  • Acetylcholinesterase inhibitors: Medications to inhibit the breakdown and destruction of acetylcholine so there is enough in the body for proper messaging between the brain and the muscles  
  • Immunosuppressants or immunomodulators: Medications to help restore the proper functioning of the immune system so that the cells stop attacking acetylcholine receptors
  • Thymectomy: Surgical removal of the thymus gland
  • Plasmapheresis: A procedure that uses a specific machine to take faulty antibodies out of blood plasma so they can be replaced with healthy ones
  • Intravenous immunoglobulin: The injection of healthy antibodies to temporarily restore the immune system to proper levels of functioning

ALS

ALS is a fatal disease. There is no cure, and treatment interventions can only improve a person's quality of life, reduce symptoms, and attempt to slow disease progression. Therapies for ALS include:

  • Medications: Current options include Riluzole and Edaravone. They aim to reduce motor neuron damage and slow down how quickly the disease progresses.
  • Physical therapy: To help improve muscle strength and mobility
  • Occupational therapy: To provide walking and movement aids to those who have lost mobility
  • Speech therapy: To teach strategies that can be used to improve verbal communication
  • Brain-computer Interface (BCI): A system that uses a wheelchair and electronic voice that is controlled by a person’s brain activity, so they do not need to physically move or speak to communicate or be mobile
  • Breathing support: Non-invasive (oxygen mask) and invasive (breathing tube) to support a person's oxygen intake

How Effective is Treatment for MG and ALS?

As mentioned above, ALS treatment can only do so much. People with the disease can participate in many therapy methods only to improve their quality of life. However, a person with MG can go into remission with effective treatment and lead everyday, symptom-free lives.

Prevention

Neither MG nor ALS can be prevented. Once someone is diagnosed with both diseases, they must undergo treatment to cope with symptoms.

Summary

While MG and ALS have some similar symptoms, the conditions are starkly different in many ways. MG is an autoimmune disorder that affects the neuromuscular junction, whereas ALS is a neurodegenerative disease.

The cause of MG is well outlined as being driven by immune system dysfunction, whereas the cause of ALS is not yet known. Genetics and environment may play a role, but researchers continue to explore exactly how and what role that is.

Diagnostic tests such as an MRI, nerve studies, and blood tests will be a part of determining if someone has either MG or ALS, and these tests are vital so that the proper treatment can begin. Since ALS and MG have drastically different outcomes, a person must begin therapy as soon as possible.

A Word from Verywell

It can be difficult coping with symptoms when you don’t know where they’re coming from or what’s causing them. That is especially true if you’re experiencing symptoms that appear to be ALS.

See your medical provider as soon as you notice any symptoms that appear to be either ALS or MG. Since MG can be treated and a person can go into remission, but ALS is fatal and progressively worsens over time, getting the correct diagnosis as quickly as possible is the best thing you can do for yourself and your health.

Frequently Asked Questions

  • Can ALS be mistaken for MG?

    Both ALS and MG can present with similar symptoms, so they can suspected simultaneously. However, the two diseases are not one and the same. Because there are starkly different symptoms, after a thorough diagnostic process, the two are unlikely to be confused with one another.

  • Are ALS and MG caused by the same thing?

    ALS and MG develop when the communication pathway between the brain and the muscles is compromised. However, the cause is not the same. In MG, the immune system is to blame for the damage. In ALS, genetics plays a role, but it is not yet clear what causes the injury to occur.

  • Can you prevent MG or ALS?

    Unfortunately, there is no way to prevent ALS or MG. Even though researchers know the cause of MG, there is no possible way to change the course of autoimmune disease. In ALS, since the cause is not yet known, it is impossible to prevent. That being said, you can protect your health by adopting healthy lifestyle habits and keeping up with them as you age.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. National Institute of Neurological Disorders and Stroke. Amyotrophic lateral sclerosis (ALS) fact sheet.

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  4. Masrori P, Van Damme P. Amyotrophic lateral sclerosis: a clinical review. Eur J Neurol. 2020 Oct;27(10):1918-1929. doi:10.1111/ene.14393

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By Angelica Bottaro
Angelica Bottaro is a professional freelance writer with over 5 years of experience. She has been educated in both psychology and journalism, and her dual education has given her the research and writing skills needed to deliver sound and engaging content in the health space.