What is the first-line treatment for the acute phase of Myasthenia Gravis (MG)?

Treatment for Acute Phase of Myasthenia Gravis

Plasmapheresis is the first-line treatment for the acute phase of myasthenia gravis, particularly in severe cases with respiratory compromise or myasthenic crisis. 1

Treatment Algorithm for Acute Myasthenia Gravis

Severity-Based Approach:

Mild to Moderate Symptoms:

• First-line: Pyridostigmine (anticholinesterase) 30 mg orally three times daily, titrated up to maximum 120 mg four times daily based on symptom response 2
• Second-line: Add prednisone 0.5-1 mg/kg/day for persistent symptoms 2

Severe Symptoms/Myasthenic Crisis (Grade 3-4):

1. First-line: Plasmapheresis

   • Rapidly removes circulating antibodies
   • Effects typically begin within one week and last 2-4 weeks 3
   • Optimal protocol: 4-5 sessions, daily schedule preferred over alternate-day 4

2. Alternative: IVIG (Intravenous Immunoglobulin)

   • Consider when plasmapheresis is unavailable or contraindicated
   • Note: Slower onset of action compared to plasmapheresis 1
   • Typical dose: 2 g/kg divided over 2-5 days

3. Concurrent therapy: High-dose corticosteroids

   • Methylprednisolone 1-2 mg/kg IV or higher dose bolus 1
   • Note: Corticosteroids alone may initially worsen symptoms in some patients

Evidence Comparison

Plasmapheresis vs. IVIG:

• Plasmapheresis shows superior response in myasthenic crisis compared to IVIG in some patients 5
• About 75% of patients respond favorably to plasmapheresis 3
• Even seronegative patients may improve with plasmapheresis 3

Important Considerations:

• Plasmapheresis should not be performed immediately after IVIG as it will remove the administered immunoglobulin 1
• Concomitant immunosuppressive medication is recommended due to the temporary effect of plasmapheresis 3
• Factors associated with better clinical response to plasmapheresis include: high MG score, non-thymoma patients, younger age at onset 4

Cautions and Monitoring

• Monitor for respiratory function closely; hospitalization with ICU capability is recommended for myasthenic crisis 2
• If anticholinesterase agents (e.g., pyridostigmine) are used with corticosteroids, close monitoring is essential due to risk of severe weakness 6
• If possible, anticholinesterase agents should be withdrawn at least 24 hours before initiating corticosteroid therapy 6

Long-term Management

After acute phase management with plasmapheresis or IVIG, transition to maintenance immunosuppression with:

• Corticosteroids (prednisone)
• Steroid-sparing agents (azathioprine, mycophenolate mofetil, etc.) 7
• Consider thymectomy in appropriate patients

While both plasmapheresis and IVIG are effective treatments for myasthenic crisis, the evidence suggests that plasmapheresis has a more rapid onset of action and may be more effective in certain patients, making it the preferred first-line therapy for acute severe myasthenia gravis.