What is myasthenia gravis?
Myasthenia gravis (MG) is a chronic disease that causes muscle weakness fluctuating intensity.
It is a rare disease that affects one person in ten to twenty thousand. Although in some cases of myasthenia may endanger the patient’s life, the vast majority of patients can lead a normal life with proper medical treatment.
What causes myasthenia gravis?
Myasthenia is an autoimmune disease. This means that the immune system or defense, patient work over and produces antibodies to a protein that forms part of the body. This protein is called acetylcholine receptor, and is located in the membrane of muscle fibers at the junction between nerve and muscle (neuromuscular junction). Recipients serve as anchors to acetylcholine, a neurotransmitter or chemical messenger that transmits nerve impulses from the nerve to the muscle. The antibodies reduce the number of receptors on the muscle membrane and hinder the transfer. As a result, the muscle does not contract properly and patients experience weakness, especially when they use the same muscles repeatedly.Although it is now known that antibodies against the acetylcholine receptor cause muscle weakness, is still not known why they occur. Typically, patients develop antibodies after birth. In rare cases, the patient is born with a genetic abnormality that looks like myasthenia (congenital myasthenia).
Who can develop myasthenia gravis?
There are some people who inherit a tendency to develop autoimmune diseases. These people have increased risk for myasthenia gravis. In a minority of patients, the myasthenia may be associated with other autoimmune diseases like rheumatoid arthritis, lupus erythematosus, pernicious anemia and thyroid disease. Relatives of patients with myasthenia disease may also experience such.
Most patients with myasthenia have increased the remains of a gland called the thymus (thymic hyperplasia). About 10% -15% of patients have a tumor, usually benign, the thymus (thymoma).
Myasthenia gravis affects people of all races. There are approximately 1 case per myasthenia 10000-20000 inhabitants. The disease is twice as common in women than in men. Symptoms can appear at any age. Women often develop the disease in the second or third decade, and males later (in the fifth or sixth decade of life). Some children of myasthenic mothers may experience weakness during the first days of life (neonatal myasthenia), Baby-by-step anti-acetylcholine receptor.
credit to: Dra. María del Mar Carreño Martínez, Dra. Camilla Buckley, Dr. John Newsom-Davis
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