Myasthenia gravis (MG)
Myasthenia gravis, also known as MG, is a rare neuromuscular disease. The first case of MG was recorded in 1672 by Thomas Willis, an Oxford physician, at which time more information about the disease occurred and was not performed.
Types of myasthenia gravis
1) Assure your myasthenia gravis: In this disease, the immune system mistakenly attacks and destroys the cells and tissues of the body.
2) Congenital Syndromes (CMS): A term used for a group of unusual inherited choices related to muscular nerves that are different from myasthenia gravis.
:Types of autoimmune myasthenia gravis
– Myasthenia gravis ocular:
It is a type of MG in which the muscles that move the eyes and control the eyelids become easily tired and weak. Common symptoms include diplopia, drooping eyelids or closed eyes. Approximately 15% of people with MG have only eye problems. Ocular symptoms are often the first symptoms of MG, and many people may later develop other generalized muscle weakness. In about 50% of people with ocular myasthenia gravis, acetylcholine receptor (AChR) antibodies are positive in the blood test.
Generalized Myasthenia Gravis:
It is a type of MG in which the muscles outside the eye become weak. Symptoms may include, in addition to eye muscle problems, other problems such as difficulty speaking, difficulty breathing, difficulty chewing and swallowing, or difficulty performing daily tasks and general muscle weakness. Approximately 85% of people with MG have the AChR antibody present in their blood tests. Some do not have AChR antibodies in the blood, but show a small percentage of anti-MuSK (muscle kinase) antibody tests. Approximately 6% of people with MG are positive for MuSK antibodies, and most patients who are positive for MuSK antibodies suffer from the general form of myasthenia gravis. The presence and type of antibodies in the blood can help. Treatment options help for people with MG. People with anti-MuSK antibodies may have a different reaction to drugs than people with AChR antibodies.
Negative myasthenia gravis:
It is a type of MG in which antibodies (anti-AChR and anti-MuSK antibodies) are not detectable in the blood. The symptoms and response to treatment are often the same as the symptoms of AChR and MuSK antibodies. Because antibodies are not detectable in the blood, and the test results are negative, another additional diagnostic test may be needed to confirm the diagnosis of MG. Approximately 10% of people with MG are considered negative. Occasionally, antibodies are present to other proteins, such as agrin or LRP4 antibodies, meaning that these antibodies may be biomarkers of MG. With the discovery of newer antibodies to MG, fewer patients are classified as negative serum.
Diagnosis
In addition to a complete medical and neurological evaluation, a number of tests can be used to determine the diagnosis of MG once a clinical trial has begun. To check for activity-related weakness, a clinician may force the patient to perform a consistent task, such as looking up to see if drooping eyelids are exacerbated by fatigue. To test for muscle weakness, your doctor may ask you to do regular exercises with specific muscles and monitor your ability to recover and regain strength to see if it improves after a break.
The diagnosis of MG is confirmed by several methods, including:
Acetylcholine Receptor Antibody Test (AChR) –
.Blood tests to detect abnormal antibodies. Approximately 85% of people with a positive MG test are diagnosed with this group of antibodies
Anti-MuSK antibody test –
Blood test for MG patients who test negative for acetylcholine antibody (AChR). Approximately 6% of MG patients without AChR antibody are positive for anti-MUSK antibody.
Ice pack tests (ice test)
The ice pack test is an examination performed by specialists. In this test, ice is placed on the drooping eyelid for thirty seconds to one minute, and in a person with MG, the strength of the eyelid improves after the test.
Adrofonium test (Tensilon test)
Adrofonium is a drug that prevents the breakdown of acetylcholine at the synapse. In this test, after injecting the drug, the weak muscle strength improves for a limited time, for example, in drooping eyelid, the eyelid muscle strength improves and the patient is able to open the closed eye
Electromyography or nerve and muscle tape (EMG)
Repetitive nerve stimulation (RNS) using electric shocks is often used to measure muscle response and performance potential and whether the results are consistent with the diagnosis of MG.
. SFEMG
One way to diagnose a patient is MG. In this method, by recording the functional potentials of individual muscle fibers using a small needle electrode, it detects the defects of neuromuscular transmission. The results of some of these tests can be negative even for someone who may show symptoms of MG. This method is used when all tests for MG disease are negative but the doctor is still suspicious of the disease for some reason. For this reason, and due to the difficulty and pain caused by performing this method and the expensive software and the inability of all nerve tape devices to be installed on this method in a few medical centers, including in Tehran (Shariati Hospital, Imam Khomeini Hospital) , Firoozgar Hospital) is done
treatment
There are currently several treatments available to control the symptoms as well as the disease. Spontaneous recovery, although unusual, may occur without any specific treatment. However, because each MG case is unique, you and your doctor will decide on a treatment plan for your specific needs
medicines
Anti-acetylcholinesterase agents – Mestinon® (pyridio-stigmine bromide)
Allows acetylcholine to remain at the neuromuscular junction for a longer period of time, which in turn activates more receptor sites, thereby increasing conduction and muscle involvement Mestinon.
It is available in the form of 60 mg fast tablets and its Iranian type called 60 mg pyramid in Iran
A type of methionine in the form of a 180 mg slow-release capsule under the brand name Timespan delivers pyridio-stigmine bromide over a 12-hour period. 180 mg slow-release capsules in patients who need to wake up at night and take medication. It is very useful because due to the high dose and the presence of the drug in the blood, it allows the patient not to need to wake up and take the drug during the night. Of course, this type of 180 mg slow-release capsule is not currently available in Iran.
Corticosteroids and immunosuppressive agents
Corticosteroids, such as prednisolone or an immunosuppressive drug such as azathioprine or azuram (Imuran), mycophenolate mofetil (Cellcept) or cyclosporin (cyclosporin), tacrolimus (usually not widely used in Iran but used) may be used by your doctor as a medicine. Prescribe independently or in combination. These drugs inhibit the production of antibodies in your body that may block or bind to your body’s acetylcholine receptors. This blockage or binding of acetylcholine receptors causes weakness
Rituximab or Meptra
The immunosuppressive drug is by inhibiting CD20 lymphocyte cells, which is used as a second or third line alongside other immunosuppressive drugs
soliris by generic name eculizumab.
It is the latest classification of injectable drugs used to treat MG in adult patients who are positive for anti-acetylcholine receptor antibodies and works to reduce immune system attacks that may play a role in MG symptoms. Its high cost has not yet entered the Iranian market, but it is very useful in terms of treatment, and it has been useful in some patients who were resistant to retoxicap.
Other treatment strategies
Intravenous Immune Globulins (IVIG)
Your doctor may prescribe IVIG as part of your treatment regimen. A typical IVIG injection may take 4 to 8 hours and is usually in a hospital. This prevents the body from producing antibodies (which may make you weak) while protecting you from possible infections. The results are often temporary, so frequent injections are needed. This drug is used in cases of severe MG (crisis) attacks
Therapeutic plasma exchange or PLEX plasmapheresis
This is a filtration method by which abnormal antibodies are released from the blood plasma. This procedure requires two intravenous (IV) lines or ports before performing PLEX. Your doctor may decide that you need this treatment to quickly recover before surgery. Repeated PLEX treatments may be needed because your body is constantly producing antibodies.
There is usually no preference for the effectiveness of the ivig and plex methods, and the physician chooses the treatment method based on discretion and availability
Thymectomy
Removal of the thymus gland is through surgery. This method is used for patients with AchR type mg. The thymus gland is located in the middle of your chest above your heart. This gland is involved in the production of antibodies. While most active in early childhood, the thymus gland usually contracts over time and is believed to no longer function in early adulthood.
But sometimes, the thymus gland remains large and is still active in producing antibodies. The effectiveness of this surgical procedure varies from patient to patient. To improve MG-induced weakness and eliminate the thymoma, the benign tumor in the thymus, which shows up in only 10% of its patients, is removed. Anyone diagnosed with MG should have a CT scan of the breast to determine if there is a tumor
The goal of neuroectomy is to significantly improve the patient’s weakness, reduce the medications used, and ideally permanent recovery (complete elimination of all weaknesses and elimination of all medications). Thymectomy is not usually used to treat active disease, but is believed to improve long-term outcome. Results may not be seen for one to two years or more after a thymectomy.
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