Myasthenia Gravis: Frequently Asked Questions

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Myasthenia gravis, or MG, is a rare autoimmune disorder that affects communication between nerve cells and muscles, leading to weakness of the muscles you move voluntarily. It can affect anyone, but it’s most common in women younger than 40 and men older than 60. Because each person with MG experiences it differently, it’s sometimes called the “snowflake disease.” Here are some answers to key questions about myasthenia gravis.

Do the symptoms of myasthenia gravis come on gradually or suddenly?

The symptoms of MG usually worsen when you are active and improve when you rest. MG can come on suddenly, with symptoms including:

  • Ptosis (drooping eyelid)
  • Difficulty swallowing, speaking or chewing
  • Change in facial expression
  • Difficulty holding head up

How is the immune system involved in causing myasthenia gravis?

If you have myasthenia gravis, your immune system mistakenly makes antibodies that block the function of an important neurotransmitter in your muscles called acetylcholine. The antibodies do this by interfering with acetylcholine receptors, which are special proteins on the surface of muscle cells that relay signals when bound to acetylcholine. If you lack acetylcholine function, your muscles don’t get enough signals from the nerves that initiate movement. The antibodies can also block a protein that helps connect nerves and muscles, which can also lead to MG.

Some people develop myasthenia gravis from a tumor on their thymus gland, which is an important part of the immune system.

Is myasthenia gravis genetic?

What causes the body to make autoantibodies against the acetylcholine receptor is not clear. MG can run in families, but most cases occur spontaneously, without a family history. Most people who develop MG have certain variations in their human leukocyte antigen (HLA) genes, which make proteins involved in the immune system. One theory is that people with these specific HLA gene variations are predisposed to developing MG.

Most people (about 75%) with myasthenia gravis also have an abnormal thymus gland, either a greater abundance of cells or a tumor. According to research studies, the abnormal thymus may allow the abnormal autoantibodies to escape, triggering MG.

How is myasthenia gravis diagnosed?

If your doctor suspects myasthenia gravis, they will do a physical exam and check your reflexes, muscle strength, and observe you for signs like a drooping eyelid. Your doctor may also give you an injection of a chemical called edrophonium, which can make people with MG temporarily regain strength. A test with an EMG (electromyography) device can measure your nerves’ ability to send signals, and a blood test can check for the abnormal antibodies present in people with MG.

Are there different forms of myasthenia gravis?

More than 80% of cases are “generalized” myasthenia gravis, which primarily affects the extremities and the trunk. Roughly 10% of patients have ocular MG, which weakens the muscles of the eyes. Bulbar MG means your ability to speak or swallow is affected.

MG is rare in children, but babies may develop it shortly after birth due to a genetic mutation rather than an autoimmune condition. Pregnant women with myasthenia gravis may give birth to a baby with transient MG, which lasts several weeks and does not recur.

How do doctors treat MG?

Treatment for myasthenia gravis can be very effective; many people have few symptoms and some may go into remission and have no symptoms at all. There are a variety of treatments available that your doctor can recommend, including:

  • Cholinesterase inhibitors, substances that improve communication between nerves and muscles
  • Corticosteroids, steroids like prednisone suppress the immune system, which lowers antibody production
  • Immunosuppressants, medications that lower your immune system activity and are sometimes used with corticosteroids

If your symptoms worsen, there are other short-term treatments available. If a thymus tumor is causing your symptoms, doctors may remove the gland.

Is myasthenia gravis curable?

Treatment significantly improves muscle weakness in many people with MG, so they can resume most or all of their usual activities. Some people with myasthenia gravis may go into remission and have no symptoms at all - either temporarily or permanently. If a tumor on the thymus is causing your MG, removing the gland stops the symptoms and cures the disease in about half the people who have the procedure.

Is myasthenia gravis contagious?

MG is sometimes confused with the sexually transmitted disease mycoplasma genitalium because the initials are the same, but the two conditions are not related. Myasthenia gravis is not contagious.

What is a myasthenia gravis crisis?

A myasthenic crisis, when your symptoms suddenly worsen, can be life threatening. It affects your ability to breathe. If you notice increasing weakness, shortness of breath, and difficulty swallowing, contact a healthcare provider immediately. If you cannot breathe, call 911 or have someone take you to an emergency room. An MG crisis can lead to respiratory failure, and you may need a ventilator to help you breathe. Almost all myasthenic crises require prompt hospital treatment.

Can certain drugs worsen MG?

Some medicines and over-the-counter preparations may make your MG symptoms worse, so remember to tell all your healthcare providers, including dentists, about your diagnosis. Drugs that should not be used or used only under closely supervised medical care include:

  • Botulinum toxin (Botox), a compound that weakens or paralyzes muscles
  • D-penicillamine, a primary treatment for Wilson’s disease
  • Magnesium, a potentially dangerous supplement if given by IV
  • Monoclonal antibodies, man-made, biologic drugs designed as a treatment for certain diseases and which may enhance the immune system

Other “cautionary drugs” include other antibiotics, statins, beta-blockers and steroids.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Feb 24
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
  1. What is MG? Myasthenia Gravis Foundation of America.
  2. Myasthenia gravis. Mayo Clinic.
  3. Myasthenia Gravis Fact. Sheet. National Institute of Neurological Disorders and Stroke.
  4. Myasthenia Gravis. Johns Hopkins Medicine.
  5. Myasthenia Gravis. National Organization for Rare Disorders.