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Johns Hopkins Symptoms and Remedies

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Myasthenia Gravis

What is it?

Myasthenia gravis is a chronic autoimmune disorder characterized by weakness and rapid fatigue of the muscles. Antibodies, which normally fight infection, attack and inactivate muscle cell receptors that, in response to nerve impulses, permit the muscles to contract.Muscles with a reduced number of functioning receptors become weak or easily fatigable. In almost all cases, muscles behind the eye or in the face are involved first, causing double vision, drooping eyelids, and changes in speech and facial appearance. In about 85 percent of patients, muscles in the arms and legs are affected later.Muscles tend to tire after brief periods of use but recover with rest. The degree of weakness tends to fluctuate throughout the day, but is often worse in the afternoon or evening. Cycles of partial remissions alternating with debilitating relapses are common throughout the course of the disease.While there is no cure, highly effective treatments allow most patients to return to full, productive lives. The disorder may, however, become life-threatening and require emergency care in the case of myasthenic crisis, when severe muscle weakness interferes with breathing or swallowing.Myasthenia gravis most often affects women between ages 20 and 30 and, less often, men between 50 and 70.

What Causes It?

  • Myasthenia gravis occurs when, for reasons that remain unclear, antibodies produced by the body's immune system begin to inactivate receptors for acetylcholine that allow muscle fibers to respond to nerve impulses. The thymus (a gland in the chest and a component of the immune system) appears to play a role.Overgrowth of the thymus (hyperplasia) appears in 65 percent of cases, while tumors in the gland (thymomas) appear in 10 percent.

Prevention

  • There is no way to prevent myasthenia gravis.

Diagnosis

  • Patient history and physical exam. Injection of a drug that temporarily improves muscle function in myasthenia gravis patients may be given. Immediate gains in muscle strength suggest a positive diagnosis.
  • Blood tests for acetylcholine-receptor antibodies.
  • Measurement of the electrical activity of the muscles, including repetitive nerve stimulation and single fiber electromyography.
  • CT scan or MRI of the upper chest to look for thymus enlargement or a tumor.

How to Treat It

  • Acetylcholine released from nerves is rapidly inactivated by the enzyme cholinesterase. Agents that block this enzyme (anticholinesterase drugs) allow high levels of acetylcholine to persist at muscle receptor sites, thus enhancing the responsiveness to nerve impulses. These drugs alleviate symptoms but become less effective as the disease progresses.
  • Removal of the thymus (thymectomy) combined with immunotherapy results in improvement in most patients and complete remission in 35 to 50 percent.
  • Long-term use of corticosteroids, azathioprine, cyclosporine, or other immunosuppressive drugs may reduce autoimmune activity and improve strength.
  • Plasmapheresis (a procedure involving partial removal of blood plasma while blood cells are returned to circulation) may be used to remove the antibodies that inactivate muscle receptors.
  • Hospitalization and intensive care are needed in myasthenic crisis (swallowing and breathing problems).

When to Call a Doctor

  • Call a doctor if you develop the symptoms of myasthenia gravis.
  • EMERGENCY Swallowing or breathing difficulty requires immediate medical attention.