- a disease of impaired transmission of motor nerve impulses, characterized by episodic muscle weakness and easy fatigability, esp. of the face, tongue, neck, and respiratory muscles: caused by autoimmune destruction of acetylcholine receptors. Abbr.: MG[1895-1900; < NL: serious muscle weakness]
* * *Autoantibodies block the response of muscle cells to acetylcholine. Muscles weaken with repeated use but regain their strength after rest. The pattern varies, but usually muscles used in eye movements, facial expressions, chewing, swallowing, and respiration are affected first, then neck, trunk, and limb muscles. Severe cases impede breathing. Anticholinesterase drugs stimulate nerve-impulse transmission, and corticosteroids may help. Removal of the thymus has improved severe cases. Remission lasting several years may occur.
* * *chronic autoimmune (autoimmunity) disorder characterized by muscle weakness and chronic fatigue that is caused by a defect in the transmission of nerve impulses from endings to muscles (muscle).Myasthenia gravis can occur at any age, but it most commonly affects women under the age of 40 and men over the age of 60. Persons with the disease often have a higher incidence of other autoimmune disorders. Approximately 75 percent of individuals with myasthenia gravis have an abnormal thymus.Myasthenia gravis primarily affects the muscles of the face, neck, throat, and limbs. The onset of symptoms is usually gradual, with initial manifestations of the disease seen in the muscles governing eye movements and facial expressions. Weakness may remain confined to these areas, or it may extend to other muscles, such as those involved in respiration. Muscular exertion seems to exacerbate symptoms, but rest helps restore strength.The autoimmune reaction underlying myasthenia gravis results from a malfunction in the immune system in which the body produces autoantibodies (autoantibody) that attack specific receptors located on the surface of muscle cells. These receptors are found at the neuromuscular junction, where nerve cells interact with muscle cells. Under normal circumstances, a nerve cell, stimulated by a nerve impulse, releases the neurotransmitter acetylcholine, which crosses the neuromuscular junction and binds to receptors on the muscle cell, thus triggering a muscular contraction. In myasthenia gravis, autoantibodies bind to the receptors, preventing acetylcholine from binding to them and thus preventing the muscle from responding to the nerve signal.Treatments (therapeutics) for myasthenia gravis include anticholinesterase medications, which stimulate the transmission of nerve impulses, and corticosteroids (corticoid), such as prednisone, which dampen the immune response. Removal of the thymus often results in improvement.
* * *
Look at other dictionaries:
Myasthenia gravis — Classification and external resources Detailed view of a neuromuscular junction: 1. Axon 2. Sarcolemma 3. Synaptic vesicle 4. Nicotinic acetylcholine receptor 5. Mitochondrion … Wikipedia
myasthenia gravis — myasthenia gra·vis grav əs, gräv n a disease characterized by progressive weakness and exhaustibility of voluntary muscles without atrophy or sensory disturbance and caused by an autoimmune attack on acetylcholine receptors at neuromuscular… … Medical dictionary
myasthenia gravis — [mī΄as thē′nē əgrā′vis] n. a disease of faulty nerve conduction characterized by myasthenia, esp. of the face and neck … English World dictionary
Myasthenia gravis — Klassifikation nach ICD 10 G70 Myasthenia gravis und sonstige neuromuskuläre Krankheiten G70.0 Myasthenia gravis … Deutsch Wikipedia
Myasthenia Gravis — Klassifikation nach ICD 10 G70 Myasthenia gravis und sonstige neuromuskuläre Krankheiten G70.0 Myasthenia gravis … Deutsch Wikipedia
Myasthenia gravis — Myasthénie La myasthénie ou myasthénie grave (MG, en latin myasthenia gravis = grave faiblesse musculaire ) est une maladie neuromusculaire de la musculature striée squelettique par atteinte de la transmission neuro musculaire entraînant une… … Wikipédia en Français
Myasthenia gravis (MG) — An autoimmune neuromuscular disorder characterized by fatigue and exhaustion of muscles. It is caused by a mistaken immune response to the nicotinic acetylcholine receptors (AChR), which are found in junctions between muscles and the nervous… … Medical dictionary
myasthenia gravis — a chronic disease marked by abnormal fatigability and weakness of selected muscles, which is relieved by rest. The degree of fatigue is so extreme that these muscles are temporarily paralysed. The muscles initially affected are those around the… … The new mediacal dictionary
myasthenia gravis — noun Etymology: New Latin, literally, grave myasthenia Date: 1900 a disease characterized by progressive weakness and exhaustibility of voluntary muscles without atrophy or sensory disturbance and caused by an autoimmune attack on acetylcholine… … New Collegiate Dictionary
myasthenia gravis — The characteristic feature of the disease is easy fatigue of certain voluntary muscle groups on repeated use. Muscles of the face or upper trunk are especially likely to be affected. In most, and perhaps all cases due to the development of… … Dictionary of molecular biology