Myasthenia gravis

Myasthenia gravis (MG, Latin: "grave muscle weakness") is a neuromuscular disease leading to fluctuating weakness and fatiguability. It is one of the best known autoimmune disorders and the antigens and disease mechanisms have well been identified. Weakness is caused by circulating antibodies that block acetylcholine receptors at the post-synaptic neuromuscular junction, inhibiting the stimulative effect of the neurotransmitter acetylcholine. Myasthenia is treated with immunosuppression and cholinesterase inhibitors.

Treatment

Myasthenia gravis can usually be controlled with medication. Medication is used for two different endpoints:

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• Direct improvement of the weakness
• Reduction of the autoimmune process

Muscle function is improved by cholinesterase inhibitors, such as neostigmine and pyridostigmine. These slow the natural enzyme cholinesterase that degrades acetylcholine in the motor end plate; the neurotransmitter is therefore around longer to stimulate its receptor.

Related Topics:
Cholinesterase inhibitor - Neostigmine - Pyridostigmine - Cholinesterase

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Immunosuppressive drugs such as prednisone, cyclosporin and azathioprine may be used. If the myasthenia is serious (myasthenic crisis), plasmapheresis is used to remove the putative antibody from the circulation. Similarly, intravenous immunoglobulins (IVIg) is used to bind the circulating antibodies.

Related Topics:
Prednisone - Cyclosporin - Azathioprine - Plasmapheresis - Intravenous immunoglobulin

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Thymectomy, the surgical removal of the thymus gland (which is abnormal in myasthenia gravis patients), improves symptoms in more than 50 percent of patients, even in those without thymoma. Some patients are cured by thymectomy, suggesting that the thymus plays a significant role in the pathogenesis of myasthenia.

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