![]() Weakness in arms, legs, fingers, hands or neck.Jaw muscles that tire easily, such as when chewing gum or meat.A change in facial expressions, such as a smile that looks more like a grimace.Muscle weakness that seems better in the morning or after resting and worse after activity or at the end of the day.Muscles that become progressively weaker with prolonged use.Symptoms may include some or all of the following: These symptoms can take many forms, and the symptoms may be more or less severe for different people. The primary symptoms of myasthenia gravis are that muscles are weak and tire quickly. Usually the baby's symptoms go away within a few weeks after birth. This probably is because the baby acquires the antibodies that attack the body's cells from the mother during gestation. The thymus is abnormal in about 80% of people with myasthenia gravis enlargement is the most common abnormality but about 10% to 15% of people with the disease have a benign (noncancerous) tumor of the thymus.Īlthough myasthenia gravis is not believed to be inherited or contagious, babies born to mothers who have myasthenia gravis have an increased risk of having the disease at birth. ![]() The thymus gland is thought to be the site of abnormal antibody production in myasthenia gravis, although its precise role is not yet understood. The thymus, a gland located in the chest just above the heart, is involved in immunity early in life. No one knows what causes the body to attack its own cells. The person may need a breathing tube and a respirator. In some situations, such as during a respiratory infection, this weakness becomes severe. Sometimes, the disease affects the muscles that control breathing. In most people, the disease eventually spreads to other areas and can affect the muscles of the arms and legs. Later, facial weakness can make smiling, chewing, swallowing and talking difficult. Muscles that control the eyelids and eye movements usually are affected early in the disease. Myasthenia gravis typically strikes muscles in the face first. This is why a person with myasthenia gravis will feel strongest immediately after waking up or resting and weakest at the end of the day when muscles have been in continual use. Muscles that may seem normal at first become weak with continued use. In a person with myasthenia gravis, that normal decrease combined with fewer working receptors causes increasing weakness, or myasthenic fatigue. ![]() Normally, the amount of acetylcholine available to be released to muscle cells diminishes with repeated, prolonged or strenuous activity. It has been estimated that up to 80% of the receptors can be damaged in this disease. ![]() Therefore, muscles do not contract properly and become weak. Some of the receptors are destroyed or blocked, which means that the chemical message cannot be received. In myasthenia gravis, the immune system attacks the acetylcholine receptors with specific antibodies. Myasthenia gravis is an autoimmune disease, which means the body's defense mechanism, the immune system, begins to attack the body's own tissues instead of foreign invaders, such as viruses. This chemical binds to special acetylcholine receptors on the muscle cells and causes the muscle to contract. Nerve signals cause the nerve endings to release a chemical called acetylcholine into the small space between the nerve and the muscle. Normal muscle movement relies on chemical signals from the nerves. After age 50, men are more likely to get the disease. The disease can occur at any age, but it mainly affects women between ages 20 and 40. Myasthenia gravis is a chronic (long-lasting) and rare disease that affects the way muscles respond to signals from nerves, leading to muscle weakness. ![]()
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