What is Myasthenia Gravis (MG)?
Myasthenia gravis is a chronically occurring neuromuscular autoimmune disorder in which weakness occurs in the skeletal muscles. An autoimmune disorder is when the immune system attacks the body’s receptors. The associated weakness worsens after activity and improves after rest.
The term myasthenia gravis has both Greek and Latin origins, meaning “serious or grave muscle weakness.” Although no cure has been found for this autoimmune disease, existing treatments have made myasthenia gravis manageable. With current therapies, the symptoms of the disorder can be controlled, allowing patients to experience an improved quality of life.
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Causes of Myasthenia Gravis
Neurotransmitters are chemicals released by nerves to communicate with the muscles. These neurotransmitters attach onto receptors over the muscle cells at the nerve-muscle junction.
Myasthenia gravis occurs when your immune system causes your antibodies to damage or block acetylcholine receptor sites for your muscles. As a result, very few receptor sites are available, and fewer nerve signals are received by your muscles, leading to weakness.
This disease may also occur when antibodies restrict the activity of a protein called muscle-specific receptor tyrosine kinase (MuSK). This protein is responsible for the formation of the nerve-muscle junction, and when antibodies attack this protein, it can lead to myasthenia gravis.
Lastly, myasthenia gravis may occur when antibodies work against a protein, lipoprotein-related protein 4 (LRP4).
Studies have shown other antibodies to be involved as causative factors, and their number is expected to rise.
However, in some patients, myasthenia gravis doesn’t develop due to antibodies blocking acetylcholine, LRP4, or MuSK. This kind of condition is known as antibody-negative or seronegative myasthenia gravis. Researchers believe that while this type of myasthenia gravis doesn’t appear to involve antibodies, it still has an autoimmune basis.
Thymus Gland Disorders
The thymus gland can be found underneath the breastbone in the upper chest region as part of your immune system. Researchers believe that the thymus gland activates or mediates antibody production, which blocks acetylcholine.
The thymus gland is large in infants, and its size reduces with age, becoming small in healthy adults. However, in some people with myasthenia gravis, the size of the thymus gland becomes abnormally large. Certain patients of MG disease can also have thymus gland tumors called thymomas.
Rarely, mothers with myasthenia gravis have children who are born with the disorder (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 gravis, called congenital myasthenic syndrome.
Some factors can exacerbate myasthenia gravis. These include:
- Illness or infection
- Medications —beta-blockers, quinidine sulfate, quinidine gluconate, quinine (qualaquin), phenytoin, some anesthetics, and antibiotics
- Menstrual periods
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What Are the Symptoms of Myasthenia Gravis?
The primary symptom of myasthenia gravis includes weakness of voluntary muscles, which are muscles under your control. Muscles may fail to contract generally due to their inability to respond to nerve impulses. Because of the lack of impulse transmission, blockage occurs in the communication between muscles and nerves, resulting in weakness. This weakness generally worsens with activity and improves with rest.
Other Symptoms of MG Disease Can Include:
- Hoarse voice
- Difficulty speaking
- Facial weakness
- Problems breathing because of muscle weakness
- Difficulty swallowing
- Double vision
- Drooping of eyelids
These symptoms might not necessarily be present in every patient, and the severity of muscle weakness may vary from day to day. If not treated in time, the severity of the symptoms becomes worse.
While the complications of myasthenia gravis are generally manageable, some complications can be lethal.
The weakening of the muscles that control breathing leads to a complication called myasthenic crisis. It is a life-threatening complication that happens due to the extreme fragility of these muscles. In such cases, emergency intervention along with mechanical support for breathing is required. With medicines and blood-filtering treatments, patients can start breathing on their own again.
Thymus Gland Tumors
In some patients, myasthenia gravis occurs due to a thymus gland tumor (thymoma). Although the majority of these tumors are not malignant, some may become cancerous.
Individuals who have myasthenia gravis are more susceptible to have certain other disorders, which include:
- Overactive or Underactive Thyroid. The thyroid gland, situated in the anterior part of your neck, has a key role in secreting thyroid hormone, thus regulating your metabolism. An underactive thyroid might cause problems, including feeling cold, weight gain, etc., while the overactive thyroid may cause problems with feeling excessive heat, weight loss, etc.
- Autoimmune Conditions. Individuals who have myasthenia gravis may be more prone to have autoimmune conditions such as lupus or rheumatoid arthritis.
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How Is Myasthenia Gravis Diagnosed?
Your clinician will suggest various tests for the confirmation of a myasthenia gravis diagnosis.
Physical and neurological examination
Your clinician will review medical history and carry out a physical examination. A neurological examination will include checking muscle tone and strength, coordination, sense of touch, and looking for eye movement issues.
Blood tests are done to check for elevated levels of certain antibodies in the blood, including acetylcholine receptor antibodies and anti-MuSK antibodies. However, some people with myasthenia gravis may be negative for these antibodies (they may have the seronegative type of myasthenia gravis).
Repetitive nerve stimulation may also be needed to check for the stimulation of the patient’s nerves. In patients with MG disease and with other neuromuscular disorders, muscles don’t respond to repetitive electrical stimulation as well as they do in muscles of healthy individuals. The most sensitive test for MG disease is single-fiber electromyography (EMG), which perceives diminished nerve-to-muscle transmission. This test can help to diagnose mild cases of MG when other tests do not successfully demonstrate abnormalities.
Magnetic resonance imaging (MRI) or Computed tomography (CT) of the chest can be used for the identification of thymoma or other abnormality in your thymus.
Pulmonary Function Testing
Respiratory failure can be checked by measuring breathing strength. Respiratory failure may cause a myasthenic crisis.
As weakness is a commonly occurring symptom of several disorders, a myasthenia gravis diagnosis can be delayed or missed in individuals with mild weakness or in those who have weakness locally in a few muscles.
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Treatment of Myasthenia Gravis
Several single or combination treatments may alleviate symptoms of myasthenia gravis. The treatment you will receive depends on your age, the severity of your disorder, and disease progress.
Cholinesterase Inhibitors, including pyridostigmine, are used to improve communication between muscles and nerves. These medications do not cure the condition but can enhance muscle strength and contraction in some patients. Their side effects can include diarrhea, gastrointestinal upset, nausea, and extreme sweating and salivation.
Prednisone obstructs the immune system and limits the production of antibodies. However, long-term corticosteroid use can lead to severe side effects, including weight gain, bone thinning, diabetes, and an increased risk of infections.
Immunosuppressants regulate your immune system. They include medications such as azathioprine, mycophenolate mofetil, cyclosporine, methotrexate, or tacrolimus. Adverse effects of immunosuppressants include elevated risk of infection and kidney or liver damage.
Intravenous therapy may also be used for myasthenia gravis treatment for the short term to treat rapid deterioration of symptoms. It may also be used prior to surgery.
In this process, a filtering procedure is used that is similar to dialysis. Blood is passed through a machine that eliminates the antibodies that obstruct signal transmission from the nerve endings to muscles’ receptor sites. The risks of plasmapheresis are a decrease in blood pressure, heart rhythm problems, bleeding, or muscle cramps. Some individuals may develop an allergic reaction due to the compounds found in the replacement of the plasma.
Intravenous Immunoglobulin (IVIG)
Your body gets normal antibodies with IVIG treatment, which plays a role in altering your immune response. Benefits are usually seen within a week and may last for 3 to 6 weeks. Side effects are typically mild and can include dizziness, chills, fluid retention, and headaches.
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Some individuals with MG disease may have a thymus gland tumor. In such cases, a thymectomy will be performed (i.e., surgical removal of the thymus gland).
Even in the absence of a thymus gland tumor, thymectomy may improve myasthenia gravis symptoms. Nonetheless, thymectomy benefits may take some years to show progress.
The thymectomy procedure involves open or minimally invasive surgery. The open surgery procedure involves the splitting of the sternum (central breastbone) for opening your chest and removing the thymus gland.
Minimally invasive surgery to remove the thymus gland uses smaller incisions. It might also involve:
- Video-assisted Thymectomy. Either a small incision is placed on your neck, or a few small incisions are made on the side of the chest. A long, thin camera called a video endoscope is used to view and remove the thymus gland.
- Robot-assisted Thymectomy. Small incisions are placed on the side of your chest for the removal of the thymus gland with the help of a robotic system that comprises a camera arm as well as mechanical arms.
Minimally invasive procedures may cause less pain, less blood loss, lower mortality rates, and shorter hospital stays compared to open surgery.
Lifestyle and Home Remedies
You should adjust your lifestyle to make the most of your energy and help cope with the symptoms of myasthenia gravis.
Adopt the Right Eating Routine
Chew your food properly and eat your meals when you have good muscle strength. Try to take breaks between bites. Eating smaller portions a couple of times a day might also help. In addition, eat soft foods and avoid hard foods that require more chewing.
Practice Safety Precautions at Home
Try to prevent falls by installing railings or grab bars in areas where support is needed, including next to the stairs or bathtub. Your floors should be kept tidy, and remove area rugs. Keep your sidewalks and driveways clear of snow, leaves, and other rubble that may cause you to trip.
Utilize Electric Appliances and Tools
To preserve your energy, use electric can openers, electric toothbrushes, and other electrical appliances for performing tasks.
Wear an Eye Patch
Eye patches can help alleviate double vision. Wear an eye patch, especially when writing, reading, or watching TV. Also, you should shift the eye patch to the other eye periodically to reduce eyestrain.
Shopping or other tasks should be planned when you have the most energy.
Coping and Support
Living with myasthenia gravis can be challenging as it turns the body against itself. The condition can worsen due to stress, so you should explore methods to help you relax. Don’t hesitate to ask for help when needed.
- Anonymous. Myasthenia Gravis. John Hopkins Medicine. https://www.hopkinsmedicine.org/health/conditions-and-diseases/myasthenia-gravis
- Mayoclinic staff. Myasthenia Gravis. Mayoclinic. Jun 2021. https://www.mayoclinic.org/diseases-conditions/myasthenia-gravis/symptoms-causes/syc-20352036
- NIH Staff. Myasthenia Gravis Fact Sheet. NIH. Apr 2020. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Myasthenia-Gravis-Fact-Sheet+
- Weatherspoon D. Myasthenia Gravis. Healthline. Sept 2018. https://www.healthline.com/health/myasthenia-gravis
Dr. Stephanie Shieh, PharmD was born in Kentucky and raised in Southern Los Angeles. She attended the Western University of Health Sciences and has been a practicing pharmacist for 7 years. The most rewarding part of her job is seeing her patients happy – whether it’s helping them understand their medication, catching a drug interaction, or being able to communicate with their doctor to improve their therapy. She is currently precepting students from Marshall B. Ketchum University. In her free time, she enjoys spending quality time with her husband and 2 daughters. They love playing outside, doing arts and crafts, and having family dinner.