Myasthenia Gravis - Summary
• an autoimmune disease of the postsynaptic neuromuscular junction associated with antibodies to the postsynaptic acetylcholine receptors
• Onset: third decade of life in women and after age 50 years in men
Diagnosis:
• Based on clinical, serologic, and EMG findings
• Disease-specific antibodies are found in 90% of patients;
- 85% have typical MG with acetylcholine receptor antibodies,
- but 5% have anti—muscle-specific kinase (MuSK) antibodies
- MuSK-positive myasthenia: More likely to cause focal or severe bulbar, cervical, or respiratory weakness.
• The characteristic EMG finding of MG is a decremental response to repetitive stimulation.
• All patients with MG should undergo chest CT to screen for thymoma, a tumor associated with the disease.).
Treatment:
• Symptomatic treatment Of ocular and mild generalized myasthenia usually
• Starts with the cholinesterase inhibitor pyridostigmine.
• In those with more advanced disease, immunosuppressive therapy is required.
- 1st line: Oral glucocorticoids - can cause transient exacerbation at high doses and should be titrated upward slowly in patients with mild to moderate weakness.
- In the presence of prominent bulbar or generalized weakness and in myasthenic crisis, treatment with IVIG or plasmapheresis should precede initiation of glucocorticoids.
• The immunosuppressant agents azathioprine, mycophenolate mofetil, and cyclosporine
• Thymectomv should be performed in all patients with thymoma.
- Improves clinical outcome and reduces immunosuppression requirements in patients with generalized MG who are younger than 65 years and within 3 years of diagnosis.
Sinai Hospital of Baltimore IM Residency @SinaiBmoreIMRes
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