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Myasthenia gravis

Myasthenia gravis is a neuromuscular disorder. Neuromuscular disorders involve the muscles and the nerves that control them.

Causes

Myasthenia gravis is a type of autoimmune disorder . An autoimmune disorder occurs when the immune system mistakenly attacks healthy tissue. In people with myasthenia gravis, the body produces antibodies that block the muscle cells from receiving messages (neurotransmitters) from the nerve cell. Antibodies are proteins made by the body's immune system when it detects harmful substances. Antibodies may be produced when the immune system mistakenly considers healthy tissue a harmful substance such as in the case of myasthenia gravis.

The exact cause of myasthenia gravis is unknown. In some cases, it is linked to tumors of the thymus (an organ of the immune system).

Myasthenia gravis can affect people at any age. It is most common in young women and older men.

Symptoms

Myasthenia gravis causes weakness of the voluntary muscles. Voluntary muscles are those that are under your control. Autonomic muscles, such as the heart and the digestive tract, are usually not affected. The muscle weakness of myasthenia gravis worsens with activity and improves with rest.

The muscle weakness can lead to a variety of symptoms, including:

Exams and Tests

The health care provider performs a physical exam. This includes a detailed nervous system (neurological) examination. This may show:

  • Muscle weakness, with eye muscles usually affected first
  • Normal reflexes and feeling (sensation)

Tests that may be done may include:

Treatment

There is no known cure for myasthenia gravis. Treatment may allow you to have periods without any symptoms (remission).

Lifestyle changes often help you continue your daily activities. The following may be recommended:

  • Resting throughout the day
  • Using an eye patch if double vision is bothersome
  • Avoiding stress and heat exposure, which can make symptoms worse

Medicines that may be prescribed include:

  • Neostigmine or pyridostigmine to improve the communication between the nerves and the muscles
  • Prednisone and other medications (such as azathioprine, cyclosporine, or mycophenolate mofetil) if to suppress the immune system response, if you have severe symptoms and other medicines have not worked well.

Crisis situations are attacks of weakness of the breathing muscles. These attacks can occur without warning when either too much or too little medicine is taken. These attacks usually last no longer than a few weeks. You may need to be admitted to the hospital where you may need breathing assistance with a ventilator .

A procedure called plasmapheresis may also be used to help end the crisis. This procedure involves removing the clear part of the blood (plasma), which contains the antibodies. This is replaced with donated plasma that is free of antibodies or with other fluids. Plasmapheresis may also help reduce symptoms for 4 to 6 weeks and is often used before surgery.

Another procedure, called immunoglobulin infusion, may also be done. With this procedure, a large amount of helpful antibodies are given directly into the bloodstream.

Surgery to remove the thymus (thymectomy) may result in permanent remission or less need for medicines, especially when there is a tumor present.

If you have eye problems, your doctor may suggest lens prisms to improve vision. Surgery may also be recommended to treat your eye muscles.

Physical therapy can help maintain your muscle strength. This is especially important for the muscles that support breathing.

Some medicines can worsen symptoms and should be avoided. Before taking any medicine, check with your doctor whether it is okay for you to take.

Support Groups

You can ease the stress of illness by joining a myasthenia gravis support group . Sharing with others who have common experiences and problems can help you not feel alone.

Outlook (Prognosis)

There is no cure, but long-term remission is possible. You may have to restrict some daily activities. People who have only eye symptoms (ocular myasthenia gravis), may develop generalized myasthenia over time.

Pregnancy is possible for a woman with myasthenia gravis, but careful prenatal care is important. The baby may be temporarily weak and require medications for a few weeks after birth, but usually does not develop the disorder.

Possible Complications

The condition may cause life-threatening breathing problems. This is called a myasthetnic crisis.

Patients with myasthenia gravis have a higher risk of having other autoimmune disorders, such as thyrotoxicosis , rheumatoid arthritis , and systemic lupus erythematosus (lupus).

When to Contact a Medical Professional

Call your health care provider if you develop symptoms of myasthenia gravis.

Go to the emergency room or call the local emergency number (such as 911) if you have breathing difficulty or swallowing problems.

References

Meriggioli MN, Sanders DB. Disorders of neuromuscular transmission. In: Daroff RB, Fenichel GM, Jankovic J, Mazziotta JC, eds. Bradley’s Neurology in Clinical Practice. 6th ed. Philadelphia, Pa: Elsevier Saunders; 2012:chap 78.

Vincent A, Evoli A. Disorders of neuromuscular transmission. In: Goldman L, Schafer AI, eds. Goldman’s Cecil Medicine. 24th ed. Philadelphia, Pa: Elsevier Saunders; 2011: chap 430.

Updated: 5/28/2013

Luc Jasmin, MD, PhD, FRCS (C), FACS, Department of Neurosurgery at Cedars-Sinai Medical Center, Los Angeles CA; Department of Surgery at Los Robles Hospital, Thousand Oaks CA; Department of Surgery at Ashland Community Hospital, Ashland OR; Department of Surgery at Cheyenne Regional Medical Center, Cheyenne WY; Department of Anatomy at UCSF, San Francisco CA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team


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