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Myasthenia Gravis

Myasthenia Gravis Overview

What is Myasthenia Gravis (MG)?

Myasthenia gravis is an autoimmune disease (where the immune system attacks the body in some way). Examples of other autoimmune diseases are rheumatoid arthritis, systemic lupus erythematosis, and Graves disease. For reasons that are not understood, the body's immune system, which normally fights infections or cancers, attacks the nerve-muscle communication point.

Specifically, antibodies (proteins of the immune system) attack the acetylcholine receptor, which is on the muscle surface, and cause the signal from the nerve to be blocked.

What are the symptoms of MG?

The major symptom of MG is muscle weakness, which gets worse with activity. People with MG complain of feeling tired. Often, they may feel pretty well in the morning, but as the day goes on they become weaker. The most common problems are double vision and drooping eyelids (ptosis).

Patients often develop:

How common is MG?

Approximately 50-150 people per million of the population have myasthenia gravis.

Who can get MG?

MG affects people of any age from 2 to 100. MG affects young women more than men, but both older men and women are equally affected.

What kind of doctor should a person with MG see?

A person should see his/her family doctor and mention his/her concerns about the disease. Neurologists (doctors who are experts in the area of the nervous system) are the most qualified to diagnose and treat MG. If the symptoms are limited to the eyes, ophthalmologists (eye doctors who have been to medical school) may take care of myasthenics. Because MG is not a common disease, many doctors are not familiar with the diagnosis and treatment of MG.

Diagnosis and Treatment

What kind of tests are there for MG?

A complete history and physical examination is the first step.

Tensilon Test-- This test is given by a neurologist or ophthalmologist in the office. An intravenous (IV) line (intravenous-within a vein) is placed in the arm to allow the doctor to put a chemical called Tensilon (edrophonium) into a vein and watch for improvement in muscle strength. It is best if the physician looks for improvement in the strength of an eyelid or muscle that moves the eye. Immediate improvement of strength after injection of Tensilon tends to support a diagnosis of MG. The effects of Tensilon last only a few minutes.

Blood test for Acetylcholine Receptor Antibodies-- Not every patient with MG has antibodies that can be detected in the blood, and the level of antibodies are not correlated, or tied to, how bad your disease is. For example, a high level of antibodies does not necessarily mean a severe case of MG. On the other hand, a person with a low level of antibodies could have a severe case of MG.

An electromyogram (EMG) tests the function of nerves and muscles-- The EMG can provide a great deal of information about how the nervous system works. The examiner first stimulates a nerve with a small electric shock. A needle is then inserted into several muscles to find out how they are working. To test for MG, repeated electrical stimulation of a nerve is done, and the response of the muscle is measured. Not all patients with MG will show abnormalities or decreased response on an EMG.

Single-fiber EMG is a specialized type of EMG-- A fine needle is placed in a muscle and electrical activity is measured. This test will be abnormal in most patients with MG.

For more information, see What are the Tests for Myasthenia Gravis?

What is the thymus and what is a thymectomy?

For more information, see What is the Role of the Thymus and Thymectomy in Myasthenia Gravis?

What treatments are there for double vision and a drooping eyelid?

What treatments are available for MG?

There are a variety of treatments for MG. The choice of treatments is based on:

Treatment decisions should be made after the patient has a more complete understanding of the disease, the treatment options available, and the potential side effects or complications of treatment.

If a patient's symptoms are not adequately treated with Mestinon, the next step is to try therapies that suppress the immune system. These therapies include:

For more information, see What Should I know About Treatment for Myasthenia Gravis?

For more information:

Go to the Myasthenia Gravis health topic, where you can:

Last Reviewed: Dec 29, 2003

Formerly, Professor of Neurology
School of Medicine
Case Western Reserve University