Myasthenia gravis is an autoimmune disease that causes muscle weakness, starting with the eye muscles. It can progress to affect the face, mouth, throat, limbs, and chest, causing difficulty with speech, swallowing, and breathing. The disease is caused by antibodies that damage or block muscle receptors, preventing acetylcholine from attaching. Symptoms worsen with activity and can be treated with drugs or surgery.
Myasthenia gravis is a disease in which the immune system works against the body, causing problems with muscle function. Muscle weakness occurs, and the eye muscles are usually affected first, leading to ptosis or droopy eyelids and double vision or diplopia. Symptoms of myasthenia gravis can spread to involve the muscles of the face, mouth, and throat, causing slurred speech or dysarthria and difficulty swallowing, or dysphagia. Finally, muscles in the limbs and chest may be affected, and if the disease is severe, weakness in the respiratory muscles may make breathing difficult. This is known as a myasthenic crisis and artificial ventilation may be required.
Normally, the brain sends signals along the nerves to make the muscles contract. There’s a small gap between the end of a nerve and the muscle it supplies, and a chemical known as acetylcholine travels through the gap and attaches itself to special receptors on the muscle, triggering the contraction. When a person has myasthenia gravis, the body produces antibodies that damage or block muscle receptors, preventing acetylcholine from attaching there. This makes it more difficult for the muscle to contract, and as a result, the person experiences the symptoms of myasthenia gravis resulting from muscle weakness.
Symptoms of ocular myasthenia gravis, involving weakness of the eye muscles, are experienced by about 90 percent of people with the disease. In a minority of cases, the signs and symptoms of myasthenia will only affect the eyes, causing droopy eyelids and double vision, but in most people, the disease progresses within about three years and becomes generalized, with muscle weakness occurring throughout the eye. body. Involvement of the face, mouth and throat can lead to loss of facial expression and can alter the voice, making it quieter or more nasal.
Difficulty chewing and swallowing can cause choking or regurgitation of food, and weakness in the neck can cause the head to hang down. Weak leg muscles can affect walking, causing a waddling gait, and it can be difficult to use your arms. When myasthenia gravis affects the respiratory muscles, coughing and chest infections can occur.
The symptoms of myasthenia gravis tend to increase with activity, when the muscles are used repeatedly. Typically, this means that muscle weakness is greatest at the end of the day or right after exercise. Rest leads to improvement of myasthenia gravis symptoms. The severity of symptoms varies widely between individuals, but the disease tends to progress over the first few years.
To treat the disease, drugs to increase the amount of acetylcholine or suppress the immune system may be used. Sometimes the thymus, a gland that produces the antibodies that cause disease, is surgically removed. Treatment of myasthenia gravis is usually successful, and people generally continue to lead normal lives.
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