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.

Eye muscles

In more than half the people who develop myasthenia gravis, their first signs and symptoms involve eye problems, such as:

  • Drooping of one or both eyelids (ptosis).
  • Double vision (diplopia), which may be horizontal or vertical, and improves or resolves when one eye is closed.

Face and throat muscles

In about 15 percent of people with myasthenia gravis, the first symptoms involve face and throat muscles, which can cause:

  • Altered speaking. Your speech may sound very soft or nasal, depending upon which muscles have been affected.
  • Difficulty swallowing. You may choke very easily, which makes it difficult to eat, drink or take pills. In some cases, liquids you're trying to swallow may come out your nose.
  • Problems chewing. The muscles used for chewing may wear out halfway through a meal, particularly if you've been eating something hard to chew, such as steak.
  • Limited facial expressions. Your family members may comment that you've "lost your smile" if the muscles that control your facial expressions have been affected.

Neck and limb muscles

Myasthenia gravis can cause weakness in your neck, arms and legs, but this usually happens along with muscle weakness in other parts of your body, such as your eyes, face or throat.

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

Talk to your doctor if you have difficulty:

  • Breathing
  • Seeing
  • Swallowing
  • Chewing
  • Walking
  • Using your arms or hands
  • Holding up your head

Antibodies

Your nerves communicate with your muscles by releasing chemicals (neurotransmitters) that fit precisely into receptor sites on the muscle cells at the nerve-muscular junction.

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.

Thymus gland

Researchers believe that the thymus gland, a part of your immune system situated in the upper chest beneath your breastbone, may trigger or maintain the production of the antibodies that block acetylcholine.

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).

Other causes

Some people may have myasthenia gravis that isn't caused by antibodies blocking acetylcholine or the muscle-specific receptor tyrosine kinase. This type of myasthenia gravis is called antibody-negative myasthenia gravis. Antibodies against another protein, called lipoprotein-related protein 4, may play a part in the development of this condition.

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

  • Fatigue
  • Illness
  • Stress
  • Extreme heat
  • Some medications — such as beta blockers, quinidine gluconate, quinidine sulfate, quinine (Qualaquin), phenytoin (Dilantin), certain anesthetics and some antibiotics

Complications of myasthenia gravis are treatable, but some can be life-threatening.

Myasthenic crisis

Myasthenic crisis is a life-threatening condition that occurs when the muscles that control breathing become too weak to do their jobs. Emergency treatment is needed to provide mechanical assistance with breathing. Medications and blood-filtering therapies help people to again breathe on their own.

Thymus tumors

About 15 percent of people with myasthenia gravis have a tumor in their thymus, a gland under the breastbone that is involved with the immune system. Most of these tumors, called thymomas, aren't cancerous (malignant).

Other disorders

People with myasthenia gravis are more likely to have the following conditions:

  • Underactive or overactive thyroid. The thyroid gland, which is in the neck, secretes hormones that regulate your metabolism. If your thyroid is underactive, you may have difficulties dealing with cold, weight gain and other issues. An overactive thyroid can cause difficulties dealing with heat, weight loss and other issues.
  • Autoimmune conditions. People with myasthenia gravis may be more likely to have autoimmune conditions, such as rheumatoid arthritis or lupus.

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

To make the most of your appointment, write lists of important information, including:

  • Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
  • Bring a list of all medications, vitamins or supplements that you're taking.
  • Write down questions to ask your doctor.

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:

  • What is likely causing my symptoms?
  • Other than the most likely cause, what are other possible causes for my symptoms?
  • What kinds of tests do I need?
  • What is the most appropriate course of action?
  • What are the alternatives to the primary approach that you're suggesting?
  • I have these other health conditions. How can I best manage them together?
  • Are there any restrictions that I need to follow?
  • Are there any brochures or other printed material that I can take home with me? What websites do you recommend visiting?

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

Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over any points you want to spend more time on. Your doctor may ask:

  • When did you first begin experiencing symptoms?
  • Have your symptoms been continuous or occasional?
  • How severe are your symptoms?
  • What, if anything, seems to improve your symptoms?
  • What, if anything, appears to worsen your symptoms?

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:

Neurological examination

Your doctor may check your neurological health by testing your:

  • Reflexes
  • Muscle strength
  • Muscle tone
  • Senses of touch and sight
  • Coordination
  • Balance

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 test

Injection of the chemical edrophonium chloride (Tensilon) may result in a sudden, although temporary, improvement in your muscle strength. This is an indication that you may have myasthenia gravis.

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

If you have a droopy eyelid, your doctor may conduct an ice pack test. In this test, a doctor places a bag filled with ice on your eyelid. After two minutes, your doctor removes the bag and analyzes your droopy eyelid for signs of improvement. Doctors may conduct this test instead of the edrophonium test.

Blood analysis

A blood test may reveal the presence of abnormal antibodies that disrupt the receptor sites where nerve impulses signal your muscles to move.

Repetitive nerve stimulation

In this nerve conduction study, doctors attach electrodes to your skin over the muscles to be tested. Doctors send small pulses of electricity through the electrodes to measure the nerve's ability to send a signal to your muscle.

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)

Electromyography (EMG) measures the electrical activity traveling between your brain and your muscle. It involves inserting a fine wire electrode through your skin and into a muscle.

In a single-fiber EMG, doctors test a single muscle fiber. Most people find this test to be uncomfortable.

Imaging scans

Your doctor may order a CT scan or an MRI to check if there's a tumor or other abnormality in your thymus.

Pulmonary function tests

Your doctor may perform pulmonary function tests to evaluate whether your condition is affecting your breathing.

Doctors use a variety of treatments, alone or in combination, to relieve symptoms of myasthenia gravis.

Medications

  • Cholinesterase inhibitors. Medications such as pyridostigmine (Mestinon) enhance communication between nerves and muscles. These medications don't cure the underlying condition, but they may improve muscle contraction and muscle strength.

    Possible side effects may include gastrointestinal upset, nausea, and excessive salivation and sweating.

  • Corticosteroids. Corticosteroids such as prednisone inhibit the immune system, limiting antibody production.

    Prolonged use of corticosteroids, however, can lead to serious side effects, such as bone thinning, weight gain, diabetes and increased risk of some infections.

  • Immunosuppressants. Your doctor may also prescribe other medications that alter your immune system, such as azathioprine (Imuran), mycophenolate mofetil (CellCept), cyclosporine (Sandimmune, Neoral) or tacrolimus (Prograf).

    Side effects of immunosuppressants can be serious and may include nausea, vomiting, gastrointestinal upset, increased risk of infection, liver damage and kidney damage.

Therapy

  • Plasmapheresis (plaz-muh-fuh-REE-sis). This procedure uses a filtering process similar to dialysis. Your blood is routed through a machine that removes the antibodies that block transmission of signals from your nerve endings to your muscles' receptor sites. However, the beneficial effects usually last only a few weeks.

    After repeated treatments, it may be difficult for doctors to gain access to your vein. They may need to implant a long, flexible tube (catheter) into your chest to conduct the procedure.

    Other risks associated with plasmapheresis include a drop in blood pressure, bleeding, heart rhythm problems or muscle cramps. Some people may also develop an allergic reaction to the solutions used to replace the plasma.

  • Intravenous immunoglobulin (IVIg). This therapy provides your body with normal antibodies, which alters your immune system response.

    IVIg has a lower risk of side effects than do plasmapheresis and immune-suppressing therapy. However, it may take about a week to start working, and the benefits usually last no more than three to six weeks.

    Side effects, which usually are mild, may include chills, dizziness, headaches and fluid retention.

Surgery

About 15 percent of the people with myasthenia gravis have a tumor in their thymus gland, a gland under the breastbone that is involved with the immune system. If you have a tumor, called a thymoma, doctors will conduct surgery to remove your thymus gland (thymectomy).

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:

  • Video-assisted thymectomy. In one form of this surgery, surgeons make a small incision in your neck and use a long thin camera (video endoscope) and small instruments to visualize and remove the thymus gland through your neck.

    Alternatively, surgeons may make a few small incisions in the side of your chest. Doctors use a video scope and small instruments to conduct the procedure and remove the thymus gland through these incisions.

  • Robot-assisted thymectomy. In a robot-assisted thymectomy, surgeons make several small incisions in the side of your chest. Surgeons conduct the procedure to remove the thymus gland using a robotic system, which includes a camera arm and mechanical arms.

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:

  • Your age
  • Severity of your condition
  • Location of muscles affected
  • Other existing medical conditions

Supplementing your medical care with these approaches may help you make the most of your energy and cope with the symptoms of myasthenia gravis:

  • Adjust your eating routine. Try to eat when you have good muscle strength. Take your time chewing your food, and take a break between bites of food. Small meals eaten several times a day may be easier to handle. Also, try eating mainly soft foods and avoid foods that require more chewing, such as raw fruits or vegetables.
  • Use safety precautions at home. Install grab bars or railings in places where you may need support, such as next to the bathtub or next to steps. Keep your floors clean, and move any loose rugs out of areas where you may walk. Outside your home, keep paths, sidewalks and driveways cleared of leaves, snow and other potential debris that could cause you to stumble.
  • Use electric appliances and power tools. You may lose energy quickly when conducting tasks. Try using an electric toothbrush, electric can openers and other electrical tools to perform tasks when possible.
  • Wear an eye patch. Consider wearing an eye patch if you have double vision, as this can help relieve the problem. Try wearing the eye patch while you write, read or watch television. Periodically switch the eye patch to the other eye to help reduce eyestrain.
  • Plan. If you have chores, shopping or errands to do, plan the activity to coincide with the time at which you have the most energy. Also, try to reduce extra walking in your house when working on projects, as it may reduce your energy.

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.

  • Experience. Mayo Clinic doctors trained in nervous system conditions (neurologists), chest surgeons (thoracic surgeons) and other specialists have extensive experience in diagnosing and treating myasthenia gravis. Doctors also have experience treating rare, hereditary forms of myasthenia called congenital myasthenic syndromes.
  • Team approach. Neurologists work with an integrated team of chest surgeons (thoracic surgeons), cancer specialists (oncologists) and others to evaluate your condition and determine the most appropriate treatment plan.
  • Efficient system. In Mayo Clinic's system, your testing and diagnosis usually can be done in just days.
  • Surgical experience. Mayo Clinic thoracic surgeons are experienced in treating myasthenia gravis and performing surgery to remove the thymus gland (thymectomy). At Mayo Clinic in Arizona, Florida and Minnesota, you may have the option of a minimally invasive thymectomy, which may include a video-assisted thoracoscopic surgery or robotic surgery. Not all surgical options are available at all Mayo locations.

Mayo Clinic in Rochester, Minn., ranks #1 for neurology and neurosurgery in the U.S. News & World Report Best Hospitals rankings. Mayo Clinic in Scottsdale, Ariz., is ranked among the Best Hospitals for neurology and neurosurgery, and Mayo Clinic in Jacksonville, Fla., is ranked high performing for neurology and neurosurgery by U.S. News & World Report.

At Mayo Clinic, we assemble a team of specialists who take the time to listen and thoroughly understand your health issues and concerns. We tailor the care you receive to your personal health care needs. You can trust our specialists to collaborate and offer you the best possible outcomes, safety and service.

Mayo Clinic is a not-for-profit medical institution that reinvests all earnings into improving medical practice, research and education. We're constantly involved in innovation and medical research, finding solutions to improve your care and quality of life. Your doctor or someone on your medical team is likely involved in research related to your condition.

Our patients tell us that the quality of their interactions, our attention to detail and the efficiency of their visits mean health care — and trusted answers — like they've never experienced.

Why Choose Mayo Clinic

What Sets Mayo Clinic Apart

Mayo Clinic works with hundreds of insurance companies and is an in-network provider for millions of people. In most cases, Mayo Clinic doesn't require a physician referral. Some insurers require referrals or may have additional requirements for certain medical care. All appointments are prioritized on the basis of medical need.

Doctors trained in neurology, cardiac and thoracic surgery, and hematology/oncology diagnose and treat people with myasthenia gravis at Mayo Clinic in Arizona.

For appointments or more information, call the Central Appointment Office at 800-446-2279 (toll-free) 8 a.m. to 5 p.m. Mountain Standard Time, Monday through Friday or complete an online appointment request form.

Doctors trained in neurology, cardiothoracic surgery and hematology/oncology diagnose and treat people with myasthenia gravis at Mayo Clinic in Florida.

For appointments or more information, call the Central Appointment Office at 904-953-0853 8 a.m. to 5 p.m. Eastern time, Monday through Friday or complete an online appointment request form.

Doctors trained in neurology, thoracic surgery and oncology care for children and adults with myasthenia gravis at Mayo Clinic in Minnesota. Members of the Neuromuscular Disease Group research potential new therapies.

For appointments or more information, call the Central Appointment Office at 507-538-3270 7 a.m. to 6 p.m. Central time, Monday through Friday or complete an online appointment request form.

Doctors trained in child and adolescent neurology, thoracic surgery, and oncology care for children with myasthenia gravis at Mayo Clinic in Minnesota. Doctors also have experience in diagnosing and treating congenital myasthenic syndromes.

For appointments or more information, call the Central Appointment Office at 507-538-3270 7 a.m. to 6 p.m. Central time, Monday through Friday or complete an online appointment request form.

See information on patient services at the three Mayo Clinic locations, including transportation options and lodging.

Mayo Clinic researchers in basic and clinical research work together to better understand how your immune system functions and how to most effectively treat your condition. Researchers trained in nervous system and immune system conditions (neuroimmunology), nervous system and muscle diseases (neuromuscular diseases), electromyography, and other areas study myasthenia gravis, congenital myasthenic syndromes and similar conditions.

Mayo Clinic doctors participate in trials for potential new medications and surgeries for myasthenia gravis, and you may have the opportunity to participate. Learn more about research on the neuromuscular diseases and ALS research website.

Publications

See a list of publications by Mayo Clinic doctors on myasthenia gravis on PubMed, a service of the National Library of Medicine.

Apr. 23, 2013