MG Versus MS

Reviewed by: HU Medical Review Board | Last reviewed: December 2022 | Last updated: December 2022

Myasthenia gravis (MG) is a chronic (long-term) condition that affects your muscles and causes weakness. Multiple sclerosis (MS) is also a chronic condition. MS can sometimes cause symptoms that are similar to MG, though MS can cause many more symptoms than just weakness.1-3

Both conditions also involve an overactive immune system. But there are several key differences between MG and MS that make them distinct diseases.1-3

How are MG and MS similar?

MG and MS are both autoimmune conditions. This means they are caused by an overactive immune system. In both conditions, the immune system attacks healthy areas of the body. But the parts of the body that the immune system targets are different. And, the part of the immune system that is overactive in each condition is different.1,2

However, MG and MS can cause some similar symptoms.1,2

MG impacts the muscles all over the body. It can impact any muscle, so symptoms can vary between people. Common symptoms of MG include:1

  • Double vision
  • Drooping eyelids
  • Changes to face expressions like smiles
  • Trouble speaking, swallowing, and chewing
  • Weak muscles in the neck, arms, and legs
  • Difficulty walking or using your arms or hands

MS is caused by damage to parts of the central nervous system including the brain and spinal cord. Because our nervous system has roles all over the body, MS can cause many different symptoms. Like with MG, different people with MS will have different symptoms. Symptoms may include:2

  • Numbness, tingling, or weakness in arms and legs
  • Double or blurry vision
  • Tremor
  • Bowel and bladder dysfunction
  • Stiffness (spasticity)
  • Difficulty walking
  • Slurred speech
  • Tiredness
  • Feeling dizzy
  • Problems thinking

MS and MG both do not have a cure. They also both get worse over time without treatment. In both conditions, treatment is aimed at limiting the disease by suppressing the immune system and managing symptoms. The specific treatments for both conditions are typically different. But they both may be treated with steroids.1,2

How are they different?

MG and MS are both caused by an overactive immune system attacking parts of the nervous system. But depending on which condition you have, your immune system targets different things and different parts of the immune system are overactive.1,2

In MG, the immune system attacks the communication between your nerves and muscles in your peripheral nervous system. This is the nervous system outside of your brain and spinal cord. MG damages muscle receptors, which receive signals from nerves to tell your muscles to contract. These signals are part of how the brain communicates with muscles. With fewer receptors, the muscles become weaker.1,2

In MS, the immune system attacks the covering (sheath) that protects the nerve fibers in the central nervous system. This is the nervous system inside your brain and spinal cord. This covering is called myelin. Damage to the myelin in the brain and spinal cord disrupts signals within these nerves. Over time, MS can cause permanent nerve damage.1,2

Is there a link between them?

In very rare cases, it is possible to have both MG and MS. Women may be more likely to have both MG and MS. And it is more common for people to have both conditions than would be expected by chance.3

Researchers think you may be slightly more likely to develop MS if you have MG. But they do not fully understand the reasons behind the link. They believe it could be related to risks for immune system overactivation that are similar in both conditions. This is supported by the notion that your risk for MS or MG increases slightly if you have other autoimmune diseases, such as autoimmune thyroid disease, rheumatoid arthritis, psoriasis, type 1 diabetes, or inflammatory bowel disease.3

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