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Myesthenia Gravis

Myesthenia gravis occurs at all ages, sometimes in association with a thymic tumor or thyrotoxicosis, as well as in rheumatoid arthritis and lupus erythematosus. It is commonest in young women with HLA-DR3; if thymoma is associated, older men are more commonly affected. Onset is usually insidious, but the disorder is sometimes unmasked by a coincidental infection that leads to exacerbation of symptoms. Exacerbations may also occur before the menstrual period and during or shortly after pregnancy. Symptoms are due to a variable degree of expression.

Clinical Findings

A. Symptoms and Signs: Patients present with ptosis, diplopia, difficulty in chewing or swallowing, respiratory difficulties, limb weakness, or some combination of these problems. Weakness may remain localized to Myasthenia Gravis.

Clinical examination confirms the weakness and fatigability of affected muscles. In most cases, the extraocular muscles are involved, and this leads to ocular palsies and ptosis, which are commonly asymmetric.

The diagnosis can generally be confirmed by the response to a short-acting anticholinesterase. Edrophonium can be given intravenously in a dose of 10 mg (1 mL), 2 mg being given initially and the remaining 8 mg about 30 seconds later if the test dose is well tolerated; in myasthenic patients.

Assay of serum for elevated levels of circulating acetylcholine receptor antibodies is another approachCincreasingly usedCto the laboratory diagnosis of myasthenia gravis and has a sensitivity of 80B90%. .


Medication such as aminoglycosides that may exacerbate myesthenia gravis should be avoided. Anticholinesterase drugs provide symptomatic benefit without influencing the course of the disease. Neostigmine, pyridostigmine, or both can be used, the dose being determined on an individual basis. The usual dose of neostigmine is 7.5B30 mg (average, 15 mg) taken four times daily.

Thymectomy usually leads to symptomatic benefit or remission and should be considered in all patients younger than age 60, unless weakness is restricted.

Treatment with corticosteroids is indicated for patients who have responded poorly to anticholinesterase drugs.