Myasthenia gravis is characterized by weakness and rapid fatigue of any of the muscles under voluntary control. Caused by a breakdown in the normal communication between nerves and muscles. No cure for myasthenia gravis, but treatment can relieve signs and symptoms, such as weakness of arm or leg muscles, double vision, drooping eyelids, and difficulties with speech, chewing, swallowing and breathing. Can affect people of any age, it’s more common in women younger than 40 and in men older than 60. Muscle weakness become worsens as the affected muscle is used repeatedly. Improve with rest, and muscle weakness may come and go. Myasthenia gravis symptoms tend to progress with time, become worst in few years after the onset of the disease. It can affect any of the voluntary muscles, certain muscle groups are more commonly affected than others. In more than half the people, the first signs and symptoms involve eye problems, such as: Drooping of one or both eyelids (ptosis), Double vision (diplopia), which may be horizontal or vertical, and improves or resolves when one eye is closed. In 15% of patient, the first symptoms involve face and throat muscles, which can cause: Altered speaking. Speech may sound very soft or nasal, depending upon which muscles affected. Difficulty swallowing. May choke very easily, which makes it difficult to eat, drink or take pills. In some cases, liquids trying to swallow may come out from nose. Problems chewing. The muscles used for chewing become tired during meal, particularly if eating something hard to chew, such as steak. Limited facial expressions. Patient lost his smile because the muscles that control facial expressions have been affected. Myasthenia gravis can cause weakness in neck, arms and legs, because of muscle weakness in other parts of the body, such as eyes, face or throat. Affects arms more often than legs. If affects legs, patient may waddle when walk. If neck is weak, it may be hard to hold up head. Nerves communicate with muscles by releasing chemicals (neurotransmitters) that fit precisely into receptor sites on the muscle cells at the nerve-muscular junction. In myasthenia gravis, patient immune system produces antibodies that block or destroy many of patient muscles receptor sites for a neurotransmitter called Acetylcholine. Only few receptor sites in muscles available for neurotransmitter with fewer nerve signals, resulting in weakness. Antibodies may also block the function of a protein called a muscle-specific receptor tyrosine kinase .This protein is involved in forming the nerve-muscular junction.
When antibodies block the function of this protein, it may lead to myasthenia gravis. The thymus gland, a part of immune system, may trigger or maintain the production of the antibodies that block acetylcholine. Large in infancy, the thymus is small in healthy adults. In some adults with myasthenia gravis, the thymus is abnormally large. Some people with myasthenia gravis also have tumors of the thymus (thymomas). Usually, thymomas aren’t cancerous (malignant). Some people may have myasthenia gravis that isn’t caused by antibodies blocking acetylcholine or the muscle-specific receptor tyrosine kinase. This type of myasthenia gravis is called antibody-negative myasthenia gravis. Antibodies against another protein, called lipoprotein-related protein 4, may play a part in the development of this condition. Genetic factors also may be associated with myasthenia gravis. Rarely, mothers with myasthenia gravis have children who are born with myasthenia gravis (neonatal myasthenia gravis). If treated promptly, children generally recover within two months after birth. Some children are born with a rare, hereditary form of myasthenia, called congenital my asthenic syndrome. Factors that can worsen myasthenia gravis Fatigue , illness , Stress , Some medications — such as beta blockers, quinidine gluconate, quinidine sulfate, quinine (Qualaquin), phenytoin (Dilantin), certain anesthetics and some antibiotics .
Complications of myasthenia gravis are treatable, but some can be life-threatening. My asthenic crisis is a life-threatening condition that occurs when the muscles that control breathing become too weak to do their function. Emergency treatment is needed to provide mechanical assistance with breathing. Medications and blood-filtering therapies help people to again breathe on their own. About 15 percent of people with myasthenia gravis have a tumor in their thymus, (gland involved with the immune system). Most of these tumors, called thymomas, aren’t cancerous (malignant). People with myasthenia gravis have the following conditions: Underactive or overactive thyroid. The thyroid gland, secretes hormones that regulate metabolism. If patient with thyroid is underactive, patient have difficulties dealing with cold, weight gain and other issues. An overactive thyroid can cause difficulties dealing with heat, weight loss and other issues. Autoimmune conditions. People with myasthenia gravis may be more likely to have autoimmune conditions, such as rheumatoid arthritis or lupus.
By – HOD – Dr. Mohammed Aslam
Department – Physiotherapy
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