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Myasthenia Gravis
Overview

Myasthenia gravis is a common neuromuscular disorder that occurs most likely due to a genetic defect with the immune system. It is an autoimmune disorder that just recently came to light over the last 20 years. In the United States, around 14 to 20 people out of 100,000 people have the disorder or around 60,000 cases. It is believed that the disorder affects many more people, but it tends to be underdiagnosed at this time. It is more common in women than men and hits around the 20’s to 30’s for women and age 50 for men. This article explains myasthenia gravis in detail and outlines treatments, lifestyle changes, and the complications that can occur.

What is Myasthenia Gravis?

Myasthenia gravis is a profound muscle weakness that affects the voluntary muscles in the body. It can happen to any race, any gender, at any age. Your voluntary muscles are signaled to do their job from impulses that travel through the nerves that start in your brain. When they get to the “neuromuscular junction” acetylcholine usually carries the impulse through to the muscle. With myasthenia gravis, there is a lower amount of acetylcholine receptors. This leads to muscle weakness. It is believed that the body’s own immune system destroys up to 80% of the acetylcholine receptors making it an autoimmune disorder that comes in “flares” and then periods of no symptoms.

Myasthenia Gravis Causes & Risk Factors

Myasthenia Gravis Causes & Risk Factors

The exact cause of myasthenia gravis is not yet completely understood, but researchers have found links to causes including:

Autoimmune Antibodies. Your body may form antibodies against the acetylcholine receptors and destroy them. Acetylcholine receptors help the nerve impulses get into the muscles to give them the energy to work properly, without enough acetylcholine the weakness sets in.

Antibodies made by the immune system may also block a protein that your muscles need called tyrosine kinase. It helps the neuromuscular junction work properly.

Thymus Gland Tumors. Your thymus gland is in the upper part of your chest and produces antibodies to viruses and infection. It is believed due to an autoimmune disorder or genetic defect, that the thymus may produce antibodies that damage the acetylcholine receptors. People with myasthenia gravis tend to have larger thymus glands or tumors are found on them that cause the gland to produce antibodies to the body’s own chemicals.

Genetics. Another type of MG may be caused by a genetic defect or a congenital syndrome known as, congenital myasthenic syndrome. There is a slight chance that children born to mothers with MG during pregnancy may be born with some of the antibodies and exhibit symptoms of MG for a few months after they are born.

Risk Factors That Precipitate Flares

The following factors may increase the chances of having a disease “flare” if you have MG:

Extreme heat
Being overtired
Stress
Illness
Medications. Antibiotics, seizure drugs, anesthesia, and beta blockers.

Researchers have not found any risk factors that raises the risk of actually getting MG. There may be a slightly increased chance for those with a family history, women between 20 and 40 years of age, and men over 60 years of age.

Myasthenia Gravis Symptoms

Myasthenia gravis can affect any muscle in the body that is voluntary. These include:

Eye muscles
Facial muscles
Swallowing muscles

Symptoms come on suddenly out of nowhere and include:

Muscle weakness
Trouble swallowing
Slurring of speech
Trouble breathing
Drooping of eyelids
Blurry vision
Trouble walking

When breathing muscles are affected, this is a medical emergency and needs medical attention right away.

How is Myasthenia Gravis Diagnosed?

Any signs of weakness should be evaluated by a doctor as soon as possible. Weakness can be a sign of many different conditions. It may take a while to diagnose myasthenia gravis after all other conditions have been ruled out.

The doctor will first take a look at your medical history, medications, family history, and do a medical exam. Your neurological status will be evaluated by looking at your hand and leg strength. They will also check your eye movements and sensations on your skin. If the doctor suspects MG you will need to have a few more tests to confirm.

Anti-MuSK Antibodies. This blood test checks for the antibodies that block acetylcholine. These antibodies are most often elevated in around 30 to 40 percent of people with MG. Some people do not have elevated antibody levels, but still have MG.

Edrophonium Test. If MG cannot be confirmed with antibody testing, the doctor may order a test where you are given an IV injection of edrophonium. This will temporarily relieve any muscle weakness in people who have MG. It increases the levels of acetylcholine that are available at the neuromuscular junctions in the body.

Nerve Conduction Study. The doctor will hook up electrodes that stimulate the muscles and check for weakness. With MG, the electrical stimulation does not seem to affect the muscles.

CT and MRI Scans. The doctor may order either a CT or MRI scan to check the thymus gland for tumors.

Pulmonary Function Studies. If your respiratory muscles are weak, the doctor may check your pulmonary function. This will help determine if you are at risk for respiratory failure from MG.

Myasthenia Gravis Treatment

The treatments for myasthenia gravis may vary according to your symptoms. There is no cure, but treatments can lessen the severity of the condition and relieve muscle weakness. These include:

Steroids. Corticosteroids can suppress the immune system from producing antibodies that attack the acetylcholine receptors. This can help with active flares of the disease, but doctors usually only use them short term due to side-effects like; bone loss, weight gain, risk of infection, and increased blood sugar.

Cholinesterase Inhibitors. These medications can increase muscular response to the nerve impulses. They can help the muscles contract and improve strength. Side-effects are; nausea, salivation, sweating, and stomach upset.

Immunosuppressant Medications. These may help lower the immune system response when it attacks the neuromuscular junctions. Doctor’s use drugs much like chemotherapy drugs that can have side-effects like; vomiting, upset stomach, kidney, and liver issues.

Intravenous Immunoglobulin. Intravenous immunoglobulin replaces antibodies that cause damage with healthy antibodies. It tends to “re-boot” the immune system but takes around a week to take effect and the effects last from 3 to 6 weeks. Side-effects include: headaches, chills, dizziness, and retention of fluids.

Plasmapheresis. Plasmapheresis filters the blood to remove antibodies and places clean blood without antibodies back into the body. The effects are only temporary, up to a few weeks and there are side effects including; muscle cramping, bleeding, blood pressure drops, and heart rhythm disturbances. There can also be allergic reactions to the dialysis fluid.

Surgery. If the doctor finds a tumor on the thymus, you may need to have surgery to have the thymus gland removed. Some people benefit from having the thymus gland removed even if there isn’t a tumor.

Myasthenia Gravis Lifestyle Changes

People with myasthenia gravis may find relief from symptoms with a few simple lifestyle changes. These include:

Dietary Modifications. Chewing and swallowing may be tricky during flares. Take your time to chew and eat your food and make food easier to eat by cutting it into small pieces. Eat more frequent and smaller meals throughout the day. Change to a soft food diet and avoid raw and crunchy foods.

Rest. If your muscles are weak, rest. Try not to overdo tasks or do too much. Break up tasks into small pieces and give yourself frequent rest periods. Ask for help with heavy lifting and tasks that take a lot of energy.

Think Safety. Use rails in the shower and stairs to hold onto. Keep cords and loose rugs out of your footpath so you don’t trip over them. Keep things picked up inside and out to prevent falls.

Try an Eye Patch. If you have double or blurry vision, try using an eye patch to reduce this issue. Cover one eye for a little while to let it rest and then switch the patch to the other eye. If your eyes become overstrained, give them a rest too.

Myasthenia Gravis Prognosis & Complications

Myasthenia Gravis Prognosis & Complications

Myasthenia gravis is manageable and most people live normal lives with good treatment and a healthy lifestyle. More severe cases may have life-threatening complications if left untreated. This includes severe respiratory issues that may require a mechanical ventilator.

There is also a risk of developing another autoimmune condition including; Lupus, rheumatoid arthritis, and hyperthyroidism, Grave’s Disease.

Current Research for Myasthenia Gravis

The National Institute of Neurological Disorders has ongoing research for Myasthenia Gravis. Researchers continue to learn more about the disorder and develop new treatments to help manage the illness. They continue to look for causes and the relation to the thymus gland.

They are looking into different medications and even combination therapies for MG. They have found that using some of the immunosuppressant drugs for rheumatoid arthritis along with corticosteroids can relieve symptoms during treatment. This can help suppress inflammatory reactions. They are also looking into using drugs that have antibody action against the body’s B cells, which turn into antibodies. Another treatment being investigated is stem cell transplantation for severe cases of MG and the use of immunosuppressants prior to having their own blood being harvested to transplant.

Bibliography

James F. Howard, J. M. (2015, June). MYASTHENIA GRAVIS – A SUMMARY. Retrieved from Myasthenia Gravis Foundation: https://www.myasthenia.org/HealthProfessionals/ClinicalOverviewofMG.aspx

Mayo Clinic. (2013, April 23). Causes of Myasthenia Gravis. Retrieved from Mayo Clinic: https://www.mayoclinic.org/diseases-conditions/myasthenia-gravis/basics/causes/con-20027124

National Institute of Neurological Diseases and Stroke. (2010, September 10). Myasthenia Gravis Fact Sheet. Retrieved from NIH: https://www.ninds.nih.gov/disorders/myasthenia_gravis/detail_myasthenia_gravis.htm#289513153

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