Myasthenia gravis
Myasthenia gravis produces sporadic but progressive weakness and abnormal fatigability of striated (skeletal) muscles, which are exacerbated by exercise and repeated movement but improved by anticholinesterase therapy. Usually, this disorder affects muscles innervated by the cranial nerves (face, lips, tongue, neck, and throat), but it can affect any muscle group.
Myasthenia gravis follows an unpredictable course of periodic exacerbations and remissions. (See Coping with lifelong myasthenia gravis.) There is no known cure. Drug treatment has improved the prognosis and allows patients to lead relatively normal lives, except during exacerbations. When the disease involves the respiratory system, it may be life-threatening.
Causes
Myasthenia gravis causes a failure in transmission of nerve impulses at the neuromuscular junction. Such impairment may result from an autoimmune response, ineffective acetylcholine release, or inadequate muscle fiber response to acetylcholine.
Myasthenia gravis affects 3 in 10,000 people at any age and is more
common in young women and older men.
common in young women and older men.
Teaching Checklist: Coping with lifelong myasthenia gravisTo help the patient deal with his condition, remember the following patient-teaching tips.
Help the patient plan daily activities to coincide with energy peaks.
Stress the need for frequent rest periods throughout the day. Emphasize that periodic remissions, exacerbations, and day-to-day fluctuations are common.
Teach the patient how to recognize adverse reactions and signs and symptoms of toxic reaction to an anticholinesterase (headaches, weakness, sweating, abdominal cramps, nausea, vomiting, diarrhea, excessive salivation, and bronchospasm) and to a corticosteroid (cushingoid symptoms [swelling of the face, buffalo hump], adrenal insufficiency [fatigue, muscle weakness, dyspnea, anorexia, nausea, fainting]).
Warn the patient to avoid strenuous exercise, stress, infection, and needless exposure to the sun or cold weather. All of these things may worsen signs and symptoms.
Advise the patient with diplopia that wearing an eye patch or glasses with one frosted lens may help.
For more information and an opportunity to meet myasthenic patients who lead full, productive lives, refer the patient to the Myasthenia Gravis Foundation.
This disease may coexist with immune and thyroid disorders; about 15% of myasthenic patients have thymomas. Remissions occur in about 25% of patients.
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