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Myasthenia Gravis

What is myasthenia gravis?

Myasthenia gravis is an autoimmune disease. This means that your body's defenses against infection attack your own tissue. This disease makes your muscles very weak.

How does it occur?

When you have myasthenia gravis, your immune system makes antibodies that attack the place where nerve cells connect with the muscles. The antibodies block the action of chemicals that normally transmit signals from the nerves to the muscles. This decreases nerve control of your muscles and makes it harder for you to use your muscles.

The cause of this disease is not well understood. It may begin at any age. In women it happens more often before age 40. In men it is more likely after age 60. Rarely, this disease is caused by tumors of the thymus gland (a tissue of the immune system).

What are the symptoms?

Symptoms may include:

  • muscle weakness that gets worse with activity and gets better with rest
  • tiredness
  • eye problems such as double vision or droopy eyelids
  • weakness in the muscles of the face, throat, and neck, which may cause trouble speaking, chewing, and swallowing
  • trouble performing activities that use the muscles of the arms or legs, such as climbing stairs or combing hair
  • trouble breathing because of weakness in the respiratory muscles.

Weakness, which gets worse over time, can vary from day to day. Stress, infection, or other factors can make symptoms worse. You may have symptom-free periods (remissions) followed by recurrences of symptoms (relapses).

How is it diagnosed?

Your healthcare provider will take your medical history and examine you. You may have tests such as:

  • Tensilon test. This test involves giving you a drug called Tensilon. The drug temporarily restores strength to the muscles by supplying the chemicals blocked by the disease. A positive response to this drug helps confirm the diagnosis.
  • Electromyography (EMG), which tests the function of nerves and muscles.
  • Blood tests to check for the antibodies that are causing the problem.

What is the treatment?

Treatments may include:

  • medicines that temporarily improve muscle strength by helping the muscles to receive signals from the nerves
  • taking steroids or other drugs that suppress your body's immune response
  • exchanging your plasma, the fluid part of your blood that contains antibodies, with plasma that does not have these antibodies
  • removal of the thymus gland, or removal of a tumor on the thymus gland.

Using a steroid for a long time can have serious side effects. Take steroid medicine exactly as your healthcare provider prescribes. Don’t take more or less of it than prescribed by your provider and don’t take it longer than prescribed. Don’t stop taking a steroid without your provider's approval. You may have to lower your dosage slowly before stopping it.

Plasma exchange, or plasmapheresis, is much like having kidney dialysis. Your blood will be removed from a vein. The liquid (plasma), which contains the antibodies that cause the disease, is separated and removed. Your red blood cells are then given back to you in another vein along with replacement fluid. You may have several weekly treatments until enough antibodies are removed to control your symptoms. The effects of the treatment wear off after weeks or months, so the effects are not permanent.

If your diaphragm muscles get so weak that you have trouble breathing, you may stop getting enough oxygen. When this happens, it is called a myasthenia crisis and is a medical emergency. Treatment usually requires a mechanical ventilator (breathing machine) for breathing until medicine can restore normal diaphragm strength and movement.

How long will effects last?

With treatment, you can expect to lead a nearly normal life. Sometimes muscle weakness may go away for a time. There is no cure, except in rare instances when the disease is caused by a tumor of the thymus gland and the tumor or the whole gland is surgically removed.

How can I take care of myself?

If you are on drug therapy, it is very important to take your medicine on an exact schedule. Any delay in taking medicine may leave you unable to swallow or breathe. You may want to set an alarm clock to remind you to take your medicine. These medicines should generally be taken with milk and crackers or other nonacid food.

Sedatives (tranquilizers or sleeping pills) and narcotic analgesics (pain medicines) can cause severe breathing problems. Wear a bracelet or necklace that states that you have myasthenia gravis. If you have trouble swallowing or breathing, get emergency treatment right away.

Since physical exertion may make your symptoms worse, you may have to change your activities somewhat.

You may also want to:

  • Join a support group.
  • Look for ways to help reduce stress.
  • Wear an eye patch to relieve double vision.

More information is available from:

Developed by RelayHealth.
Published by RelayHealth.
Last modified: 2010-12-07
Last reviewed: 2010-08-02
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
© 2011 RelayHealth and/or its affiliates. All rights reserved.
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