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Myasthenia gravis
Other Resources UpToDate PubMed

Myasthenia gravis

Contributors: David Brodell MD, Richard L. Barbano MD, PhD, Lowell A. Goldsmith MD, MPH
Other Resources UpToDate PubMed

Synopsis

Myasthenia gravis (MG) is a neuromuscular autoimmune disease characterized by painless, fluctuating motor weakness of voluntary muscles. Autoimmune MG may be ocular or generalized.
  • Eye movement abnormalities cause a range of symptoms from visual blurriness to frank diplopia. Ocular symptoms including asymmetric ptosis are common and among the presenting symptoms in over half of patients.
  • In generalized MG, dysphagia, dysarthria, fatigable chewing, hypophonia, neck muscle weakness, and proximal limb weakness may be prominent in addition to ocular manifestations. Diaphragm paralysis may occur in advanced stages, leading to crisis and the need for respiratory assistance.
Muscle fatigability is a hallmark; weakness worsens with activity and improves with rest / sleep. MG typically progressively worsens and then peaks several years after the first symptom. Approximately 50% of patients who present with ocular symptoms progress to generalized MG.

Autoimmune MG is thought to involve antibodies to the acetylcholine receptor (AChR-Ab), and such antibodies are detectable in approximately 80%-85% of patients. About 40% of patients who do not have AChR-Ab will have antibodies to muscle-specific tyrosine kinase (MuSK-Ab), a receptor-associated protein. About 10% of acquired cases remain seronegative; this is more common among patients with isolated ocular myasthenia. There are also congenital and juvenile forms of the disease.

In generalized MG, females are affected more frequently than males (3:2). It is somewhat more common in women under 40 and men over 60. MG is associated with other autoimmune disorders, including thymoma, thyroid disease, Hashimoto thyroiditis, scleroderma, rheumatoid arthritis, systemic lupus erythematosus, and multiple sclerosis. Additionally, in patients with MG who become pregnant, the highest risk for exacerbation occurs in the first trimester and in the acute postpartum period.

There is no cure, but MG can be managed with anti-acetylcholinesterase medications, thymectomy, and immunosuppression. Most patients have an average life span, although exacerbations of the disease can lead to intubation and even death.

Codes

ICD10CM:
G70.00 – Myasthenia gravis without (acute) exacerbation
G70.01 – Myasthenia gravis with (acute) exacerbation

SNOMEDCT:
91637004 – Myasthenia gravis

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Last Reviewed:04/30/2017
Last Updated:01/19/2022
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Myasthenia gravis
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A medical illustration showing key findings of Myasthenia gravis : Diplopia, Dysarthria, Eyelid ptosis, Recurring episodes or relapses, Dysphagia, Generalized weakness
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