Myasthenia gravis (MG) is a chronic, autoimmune condition characterized by muscular weakness and fatigue. The term has Latin and Greek word origins which literally means “serious muscle weakness.”
MG often involves the loss of voluntary control of the facial muscles, such as those around the eyes and mouth. It can present through drooping eyelids, uneven cheeks, as well as in difficulty chewing and swallowing. The disease can also hit the limbs, both arms and legs, affecting their effective functional movement.
According to the U.S. National Institutes of Health (NIH), myasthenia gravis affects 20 individuals per 100,000 of the world’s population, with observed prevalence increasing in recent decades. The noticed uptick is most probably due to heightened awareness and earlier diagnosis of the condition.
Myasthenia gravis affects more women than men and hits at different stages in life. For women, myasthenia gravis most commonly appears in patients in their 20’s and 30’s. For men, the onset is around their 50’s and 60’s.
What causes Myasthenia Gravis?
Myasthenia gravis occurs when there is a disruption in the normal interaction between nerves and the muscles they control. Typically, nerve impulses are sent to the muscles, which the latter then recognize and respond to. Muscles might receive instructions to contract, for example.
Since the nerves and the muscles don’t physically touch, this mechanism is animated by a neurotransmitter called acetylcholine. (Neurotransmitters are chemical substances released from the nerves to cross the “synaptic gap” and bridge “instructor” nerves and “responder” muscles.) The neurotransmitters then land on specific receptor sites in muscle cells and the signaled instructions are successfully passed.
In myasthenia gravis, this mechanism is severely disrupted. Acetylcholine neurotransmitters fail to reach the muscle cell because the specific receptor sites they usually bind to are either blocked, altered or destroyed. There is failure in the neuromuscular transmission and no message or instruction is received.
As mentioned, MG is an autoimmune condition. An autoimmune condition is one where instead of the immune system protecting the body from harmful elements like bacteria and viruses, it attacks the body’s own healthy cells. In the case of myasthenia gravis, the immune system produces antibodies that either block, alter or destroy the receptor sites for the neurotransmitter acetylcholine.
The thymus gland, an organ of the immune system found behind the sternum and between the lungs, is believed to be responsible for the production of acetylcholine receptor antibodies. In fact, tumors and other abnormalities of the thymus have often been associated with myasthenia gravis. (So in diagnosing and treating the condition, doctors look to the different pathologies of the thymus gland as a vital factor.)
What are the symptoms of Myasthenia Gravis?
The symptoms of myasthenia gravis stem from the failure of the muscles to react and respond to nerve impulses.
In the early stages, fatigue is often mistaken as the muscles’ regular response to demanding physical exertions. That is, weakness is to be expected after strenuous activities. The false impression is not helped by the fact that relief and recovery is experienced after sufficient rest. Generally though, the symptoms of the disease will worsen over time, until such a time they cannot be sufficiently attributed to regular fatigue.
In addition to weakness in the limbs, symptoms for myasthenia gravis include:
The patient loses voluntary control of the muscles around the face and fail to display appropriate facial expressions. Sometimes one side of the face droops, resulting in an uneven resting face. It would seem like the patient has suffered a stroke.
Vision and eye problems
A set of complications ensue when control of the muscles around the eye is compromised. There could be the onset of ptosis, or dropping of one or both eyelids. This is a very visual symptom of MG.
Diplopia, or the phenomenon of double vision, may also be experienced by the patient. The double vision could be oriented horizontally or vertically. (This symptom could be relieved by shutting one eye.)
Throat and mouth problems
Normally, a person has a wide range of motion in areas around the mouth and throat. But with MG, the patient experiences difficulty accomplishing regular tasks like speaking, chewing and swallowing.
Altered or impaired speech (dysarthria) is another sign that the patient is losing control of the muscles around the mouth. Words may come off very soft or nasal or hoarse, depending the specific muscles affected. Eating becomes a chore because the mechanism used to chew food tire out before the meal is finished. Difficulty in swallowing is as well exhibited as the patient loses control of the throat muscles.
The neck muscles, for their part, may become too weak as to create difficulties in keeping the head upright.
Difficulty in breathing
Shortness of breath is a serious sign. Muscular weakness may prove so debilitating that the mechanism for breathing becomes ineffectual. In this case, a “myasthenic crisis” is reached and the patient is unable to breathe by himself or herself. Emergency medical assistance should be provided.
Difficulty in walking
The general performance of the limbs is seriously inhibited. The patient’s regular gait is replaced by an uncomfortable waddle.
In addition to difficulties in locomotion, the patient reports difficulty in keeping the arms raised or in motion. There’s a general weakness or fatigue from the arms, hands, right up to the fingers.
How is Myasthenia Gravis Treated?
As of yet, there is no known cure for myasthenia gravis. There are, however, several treatment approaches that have been known to be sufficiently effective. The type and combination of treatments employed will be impacted by the following considerations:
The age and general health of the patient
Severity and progression of the condition
Parts of the body affected
Myasthenia gravis can be treated solely or through a combination of medication, IV therapy or surgery.
Drugs like pyridostigmine (eg. Mestinon) can be used to ensure a healthy supply of the neurotransmitter acetylcholine in the synaptic gap. This increases the chances of them finding available receptor sites in the muscle cells. Acetylcholinesterase inhibitors alleviate some of the symptoms of myasthenia gravis by facilitating the interaction between the nerves and the muscles.
As mentioned, myasthenia gravis is an autoimmune disease—which means the body itself is producing substances that lead to the complications. Corticosteroids like Prednisone limit the production of antibodies by the immune system—the same antibodies that bind, alter or damage receptor sites in muscle cells, hampering the efficacy of acetylcholine. Without antibodies blocking the neurotransmitter’s receptor sites, nerves regain control of adjacent muscles.
In the same manner, immunosuppressants also inhibit the efficacy of the body’s immune system by preventing the production of antibodies that attack acetylcholine receptor sites. Medicines like cyclosporine, methotrexate and azathioprine are often prescribed. These drugs, however, do come with side effects like vomiting, nausea and gastrointestinal distress. So a thorough discussion between doctor and patient is warranted.
Plasmapheresis works in the same manner as dialysis.
The patient’s blood passes through a machine which filters unwanted antibodies. With the plasma cleared, the neuromuscular interactions can proceed normally. The benefits last only up to a few weeks though, and just like dialysis, patients need to regularly come in for the procedure.
Intravenously administered immunoglobulins are protein compounds used as part of “rapid induction therapy.” These are used in cases of severe and rapidly progressing myasthenia gravis where there is a need to quickly subdue the immune system’s harmful activities. A myasthenic crisis, where the muscles involved in breathing have ceased to function, is such a case.
The immunoglobulins quickly work to neutralize the antibodies in the patient’s blood.
Infusions usually come in several sessions, with each session lasting a good few hours.
As part of treatment, doctors will recommend thymectomy, the removal of the patient’s thymus gland. Even in cases where the thymus seemed normal and healthy, its removal has been seen to improve the conditions of patients.
With the advanced state of today’s surgical techniques, a thymectomy can be a non-invasive surgical procedure.
Generally, myasthenia gravis is considered one of the most easily treatable autoimmune disease. The prospects for patients who undergo treatments are quite positive. With a healthy lifestyle and a supportive environment, persons with the disease can live normal and productive lives.
If you or any of your loved ones experience the signs and symptoms mentioned above, BloodWorks Lab can provide you with the most reliable diagnostic tools. We are proud to be the first laboratory in the Philippines to offer the Anti Acetylcholine Receptor (lgG) Antibody Test. The results of this test will help your doctor diagnose myasthenia gravis.
BloodWorks Lab is your one-stop shop for all your blood test needs. Our branches are in Alabang and Katipunan.