Myasthenia gravis (my-us-THEE-nee-uh GRAY-vis) is characterized by weakness and rapid fatigue of any of the muscles under your voluntary control.
Myasthenia gravis is caused by a breakdown in the normal communication between nerves and muscles.
There is no cure for myasthenia gravis, but treatment can help relieve signs and symptoms, such as weakness of arm or leg muscles, double vision, drooping eyelids, and difficulties with speech, chewing, swallowing and breathing.
Though myasthenia gravis can affect people of any age, it's more common in women younger than 40 and in men older than 60.
Muscle weakness caused by myasthenia gravis worsens as the affected muscle is used repeatedly. Because symptoms usually improve with rest, your muscle weakness may come and go. However, myasthenia gravis symptoms tend to progress over time, usually reaching their worst within a few years after the onset of the disease.
Although myasthenia gravis can affect any of the muscles that you control voluntarily, certain muscle groups are more commonly affected than others.
Face and throat muscles
Neck and limb muscles
The disorder usually affects arms more often than legs. However, if it affects your legs, you may waddle when you walk. If your neck is weak, it may be hard to hold up your head.
When to see a doctor
In myasthenia gravis, your immune system produces antibodies that block or destroy many of your muscles' receptor sites for a neurotransmitter called acetylcholine (as-uh-teel-KOH-leen). With fewer receptor sites available, your muscles receive fewer nerve signals, resulting in weakness.
Antibodies may also block the function of a protein called a muscle-specific receptor tyrosine kinase (TIE-roh-seen KIE-nays). This protein is involved in forming the nerve-muscular junction. When antibodies block the function of this protein, it may lead to myasthenia gravis. Research continues to study how the antibodies inhibiting this protein are related to the development of myasthenia gravis.
Large in infancy, the thymus is small in healthy adults. In some adults with myasthenia gravis, however, the thymus is abnormally large. Some people with myasthenia gravis also have tumors of the thymus (thymomas). Usually, thymomas aren't cancerous (malignant).
Genetic factors also may be associated with myasthenia gravis.
Rarely, mothers with myasthenia gravis have children who are born with myasthenia gravis (neonatal myasthenia gravis). If treated promptly, children generally recover within two months after birth.
Some children are born with a rare, hereditary form of myasthenia, called congenital myasthenic syndrome.
Factors that can worsen myasthenia gravis
Chemicals messengers, called neurotransmitters, fit precisely into receptor sites on your muscle cells. In myasthenia gravis, certain receptor sites are blocked or destroyed, causing muscle weakness. ...
The thymus gland, a part of your immune system situated in the upper chest beneath the breastbone, may trigger or maintain the production of antibodies that result in the muscle weakness. ...
Complications of myasthenia gravis are treatable, but some can be life-threatening.
Preparing for your appointment
You're likely to start by first seeing your family doctor or a general practitioner. You'll likely be referred to a doctor trained in nervous system conditions (neurologist) for further evaluation.
Because there's often a lot to talk about at your appointment, it's a good idea to be well prepared for your appointment. Here's some information to help you get ready for your appointment, and what to expect from your doctor.
What you can do
Your time with your doctor is limited, so preparing a list of questions ahead of time will help you make the most of your time together. List your questions from most important to least important in case time runs out. For myasthenia gravis, some basic questions to ask your doctor include:
In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment at any time that you don't understand something.
What to expect from your doctor
Tests and diagnosis
To diagnose your condition, your doctor will review your symptoms and your medical history and conduct a physical examination. Your doctor may conduct several tests, including:
The key sign that points to the possibility of myasthenia gravis is muscle weakness that improves with rest. Tests to help confirm the diagnosis may include:
Edrophonium chloride blocks an enzyme that breaks down acetylcholine, the chemical that transmits signals from your nerve endings to your muscle receptor sites.
Ice pack test
Repetitive nerve stimulation
To diagnose myasthenia gravis, doctors will test the nerve many times to see if its ability to send signals worsens with fatigue.
Single-fiber electromyography (EMG)
In a single-fiber EMG, doctors test a single muscle fiber. Most people find this test to be uncomfortable.
Pulmonary function tests
Treatments and drugs
Doctors use a variety of treatments, alone or in combination, to relieve symptoms of myasthenia gravis.
If you don't have a tumor in the thymus gland, surgery to remove the thymus gland may improve your myasthenia gravis symptoms. It may eliminate your symptoms, and you may be able to stop taking medications for your condition. However, you may not notice the benefits of a thymectomy for several years, if at all.
A thymectomy may be performed as an open surgery or as a minimally invasive surgery.
In an open surgery, your surgeon splits the central breast bone (sternum) to open your chest and remove your thymus gland.
Surgeons may perform minimally invasive surgery to remove the thymus gland, which uses smaller incisions. Minimally invasive thymectomy may include:
Benefits of these procedures may include less blood loss, less pain, lower mortality rates and shorter hospital stays compared with open surgery.
Your doctor will determine which treatment may be most appropriate for you based on several factors, including:
Lifestyle and home remedies
Supplementing your medical care with these approaches may help you make the most of your energy and cope with the symptoms of myasthenia gravis:
Coping and support
For people with myasthenia gravis and their family members, coping with the disease may be difficult.
If you have myasthenia gravis, find ways to relax. Stress may worsen your condition.
Also, ask for help with tasks if you need it. Your family and friends may be able to assist you with tasks that are difficult.
If you're a family member of someone with myasthenia gravis, try to be understanding of your loved one's emotions as he or she adjusts to the condition. Read about myasthenia gravis and learn about what your family member is experiencing.
You and your family members may benefit from participating in a support group. A support group may offer a place for you to meet people who understand what you and your family members are going through.
Last Updated: 2013-04-23
© 1998-2014 Mayo Foundation for Medical Education and Research (MFMER). All rights reserved. A single copy of these materials may be reprinted for noncommercial personal use only. "Mayo," "Mayo Clinic," "MayoClinic.com," "Mayo Clinic Health Information," "Reliable information for a healthier life" and the triple-shield Mayo logo are trademarks of Mayo Foundation for Medical Education and Research.
Terms and conditions of use