Myasthenia gravis is a chronic neuromuscular disease that causes weakness in the muscles, especially the skeletal muscles. These muscles are used for movement. It is characterized by the weakness of the muscles, and also leads to the quick fatigue of the voluntary muscles. In Myasthenia gravis, there is impairment in the communication between nerve cells and muscles. The disease is caused by the alteration of the connection between the nerves and the muscles. It’s an autoimmune disease, in which the body immune system blocks and attacks the acetylcholine receptors. These receptors are usually located at the junction between the nerves and the muscles. Impulses and signals are sent from the muscles to the nerves through this receptor. However, in Myasthenia gravis, this connection is blocked, leading to the inability of the muscles to contract. There is no cure for myasthenia gravis. However, the signs and symptoms can be managed. Physicians usually administer acetylcholinesterase inhibitors. Medications that suppress the immune system can also be prescribed. An example of this kind of drug is a corticosteroid. They help in suppressing the immune system, thereby directly reducing the activities of the antibodies. Stem cell therapy has also been used in the treatment of this disease, especially in severe cases. Autologous hematopoietic stem cells are usually used for this purpose. This disease is not common in children, but prevalent in women, especially women under the age of forty. People affected with this disease can live a normal life if the disease is well managed.
What are the signs and symptoms of Myasthenia gravis?
Myasthenia gravis typically affects the voluntary muscles. The signs and symptoms of this disease worsen, as the individual affected uses the affected muscle. Muscle weakness associated with this disease is intermittent; it deteriorates for a while, then the patient feels relieved for a period. However, the symptoms do improve after rest. This disease worsens gradually and is capable of reaching its peak, just some years after the disease started. Below are some of the symptoms of the disease;
- Eye muscles: This occurs in about two-thirds of the Myasthenia gravis cases. This is one of the initial symptoms of the disease. Patients might experience the drooping of the eyelids, and weakness of some of the eye muscles which could lead to double vision. The symptoms of the eyes usually become worse when patients perform activities such as driving, watching a movie in the cinema, studying and so on. In some cases, the muscle weakness is only present in the eyes, sparing the other muscles of the body. This isolated muscle weakness caused by this disease is called ocular myasthenia gravis. However, this type of isolated muscle weakness is mostly transient; it generally progresses to generalized muscle weakness after some years.
- Difficulty breathing: The muscle weakness also affects the skeletal muscles of the respiratory system. This makes breathing difficult.
- Eating: Myasthenia gravis also affects the muscles used in swallowing. This causes a lot of discomfort for the patients especially when they’re trying to swallow and digest food. This implies that some food would still remain in the mouth after the patient attempts to swallow food or any other material. Also, this disease impairs the function of the muscles of mastication. This would lead to problems and pain when chewing food. These symptoms are some of the earliest symptoms seen in a good percentage of Myasthenia gravis cases.
- Muscles of the head and limbs: This disease can also cause the weakness of muscles of the head and the extremities. This disease tends to affect muscles of the upper limb, such as the arm muscles, as compared to the leg muscles.
- Difficulty speaking: The auto-antibodies can also attack the muscles used in phonation. This usually alters the way affected people speak. Their speech may sound nasal, slurred or forced. This depends entirely on the muscles
- Restricted facial expressions: Sometimes, the nerves controlling the facial expressions might be affected by this disease. This would eventually lead to the loss of facial expressions, such as smiling.
What causes Myasthenia gravis?
- Autoimmunity: Myasthenia gravis is an autoimmune This is a condition in which the immune system fails to recognize the body cells and tissues, then proceeds to attack and impair its functions. This is what happens in this disease. Autoantibodies attacks and tries to destroy the acetylcholine receptors in the nerves and muscles. This would leave just a few receptors to perform the job of the transmission of impulses and signals, eventually leading to the weakness of the muscles.
- Thymus gland: Some studies and researchers have suggested that thymus gland could be a critical factor in the development of this disease. The thymus gland is located in the upper part of the chest, just behind the breastbone. The gland is part of the reticuloendothelial system. However, it has been observed that this organ might induce the production of antibodies that block the receptors communication between the nerves and the muscles. The thymus gland generally becomes smaller and might involute as one grows; however, this gland is usually large on people affected with this disease. In fact, some myasthenia gravis patients do have a tumor of the thymus gland. The symptoms of the disease can be improved by having the thymus gland removed surgically.
- Other causes: Myasthenia gravis can also be transferred from a mother to her children. This condition is known as neonatal myasthenia gravis. Although this type of myasthenia gravis is scarce, there have been reported cases.
How Is Myasthenia Gravis Diagnosed?
The physician would conduct a physical examination of the patient. Subsequently, the history of the symptoms presented by the patient would be taken. The doctor might also perform some neurological examination, which might include the following;
- Check for the weakness of the muscles.
- Checking for the eye reflexes.
- Motor functions would also be tested.
- General reflexes would also be tested.
Other tests that can help in diagnosing this disease include testing for the presence of antibodies. The name of the test is the Tensilon test. Imaging tests such as CT scan, MRI might also be done for further evaluation.
How is this disease currently treated?
Unlike most autoimmune diseases, myasthenia gravis can be cured. Below are some of the treatments that a physician could suggest;
- Medications: There are some drugs that can improve the symptoms of this disease. Top of the list is cholinesterase inhibitor. This drug does not cure the disease, but it improves the symptoms. Other includes corticosteroids, an immunosuppressant.
- Intravenous therapy
- Surgery: A fraction of those affected by myasthenia gravis do have abnormal enlargement of the thymus. This can be surgically removed.
Stem cell therapy and Myasthenia gravis
Stem cell therapy has been successfully used in the treatment of this disease. This was done by doing autologous hematopoietic stem cell transplantation. This basically means that stem cells are extracted from the bone marrow of the patient, and then transplanted into the patients. Stem cells are unique cells that are capable of differentiating into other types of cells. They can self-regenerate, and also have the ability to replace and repair any damaged or injured cell receptors, in this case.
References
Lee, I., Kaminski, H., Xin, H., & Cutter, G. (2018). Gender and quality of life in myasthenia gravis patients from the myasthenia gravis foundation of America registry. Muscle & Nerve. doi: 10.1002/mus.26104
Morren, J., & Li, Y. (2018). Myasthenia gravis with muscle-specific tyrosine kinase antibodies: A narrative review. Muscle & Nerve. doi: 10.1002/mus.26107
Sieb, J. (2014). Myasthenia gravis: an update for the clinician. Clinical & Experimental Immunology, 175(3), 408-418. doi: 10.1111/cei.12217
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