Реферат: Myasthenia Gravis Essay Research Paper Myasthenia GravisHistoryMyasthenia
Myasthenia Gravis Essay, Research Paper
Myasthenia gravis is believed to have been discovered as early as 1672 when Thomas Willis, wrote in his book De Anima Brutorum, that “a woman who temporarily lost her power of speech and became ‘mute as a fish.’”.(Abboud, 1996). Another early description of this disease is documented in colonial correspondence with England. “The excessive fatigues he encountered wrecked his constitution; his flesh became macerated; his sinews lost their tone a warrior chief. He had an elasticity and his eyelids were too heavy that he could not see unless they were lifted up by his attendants. Further, we are told that he was unable to walk; but his spirit rising above the ruins of his body, directed them from litter on which he was carried by his Indians, the onset and retreat of his warriors.” While in captivity in Jamestown he was able to rest. After this inactivity he was able to raise himself from the ground to the standing position. Perhaps this warrior in his later years had developed MG(Abboud, 1996). Both of these early descriptions describe a lack of voluntary muscles resolving in great fatigue and weakness. These are definitely signs of myasthenia gravis. So even as far back as the late 1600’s people were beginning to see some effects of myasthenia gravis and actually began to learn a little about it.
Myasthenia gravis (MG) is a disease in which muscles are quickly fatigued with repetitive use. “Myasthenia gravis is characterized by decremental neuronal response with repetitive nerve stimulation, and evidences itself in a few characteristic, physical ways.”(Addoub,1996). A person with Myasthenia Gravis has a flattened smile and droopy eyes, and slow pupil light responses. The person may have a slouched posture appearance after standing for a while. Nasal speech, difficulty chewing and swallowing, dulled facial expression, including difficulty smiling and an ineffective cough due to weak expiratory muscles, are also symptoms of MG. This disorder is also involved with vision changes, double vision, difficulty maintaining steady gaze, frequent gagging or choking, a difficulty talking or chewing, weakness or paralysis that worsens with exertion later in the day, a droopy head, along with poor posture, a difficulty climbing stairs and lifting heavy things, a need to use hands to arise from sitting position, and lastly weakness and paralysis improving with rest(Howard).
Is a group of diseases, affecting the neuromuscular junction. congenital myasthenia syndrome (CMS, or CMG) is a “cousin” disease that is genetic in nature, meaning the body has a flaw in the chromosomes(Addoub,1996). “MG involves fluctuating levels of weakness of commonly used muscles. Weakness occurs when the nerve impulse does not adequately reach the muscle cells; this is caused by blockage of the action of neurotransmitters (the specific chemicals that transmit signals from nerve cell to muscle cell). Acetylcholine RECEPTORS on the muscles are actually destroyed by the immune system, thus it is an immune response of the body against itself. High levels of antibodies block the action of neurotransmitters(Howard). Myasthenia gravis typically targets skeletal muscles, where the nicotinic acetylcholine receptors are located. The muscles innervated by the cranial nerves are often the first and worst affected(Adduob,1996)
Even though this is considered an autoimmune disorder such as this form of Myasthenia Gravis the actual cause of these autoimmune disorders is unknown. “In some cases, it may be associated with tumors of the thymus (a tissue of the immune system). It also may be associated with hyperthyroidism/thyrotoxicosis, rheumatoid arthritis, Lupus (systemic lupus erythematosus), and other immune system disorders. In many cases, no other disorder is identified”(Howard).
No cure for myasthenia gravis has been found. Therefore, the next concern would be to decrease or eliminate the symptoms that accompany the disease. The general life outlook for people with this disease has improved greatly over the years, with the mortality rate for patients with generalized myasthenia 30 percent, 31 percent showing deterioration or remaining unchanged, and only 29 percent having an improvement in their condition before 1958. Now with proper treatment, the mortality rate is essentially zero, although most patients must take immunosuppressive medication for the rest of their life. Management of myasthenia gravis varies according to the severity of the disease, the age of the patient, and the type of myasthenia the patient has. “About 10 percent of the disease?s victims die. For those who survive the first three years, there is a chance for stabilization ad even some degree of recovery”(Howard).
The main ways for treating myasthenia gravis include the use of cholinergic or anticholinestrase therapy that interfere with the activity of the enzyme acetylcholinesterase, immunosuppression therapy, removal of thethymus.
In removing the Thethymus or performing a thethymus. The goal is to induce remission or improve reduction in immunosuppressice medication. The doctors whom perform this procedure really don’t know why it helps but it does so they will do it in order to help out someone who has this disease. But it is believed that the “thymectomy produces benefits in myasthenia gravis is still uncertain. In general, acetylcholine receptor-antibody levels fall after thymectomy, although there are conflicting reports. On theoretical grounds, there are several possible mechanisms. First, removal of the thymus may eliminate a source of continued antigenic stimulation. If the thymic myoid cells are the source of autoantigen then their removal might allow the immune response to subside. Second, thymectomy may remove a reservoir of B cells that are secreting acetylcholine-receptor antibody. Third, thymectomy may is some way correct a disturbance of immune regulation in myasthenia gravis”(Howard).
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University of North Carolina at Chapel Hill