What is the recommended treatment for a patient with Myasthenia Gravis (MG), a chronic autoimmune disorder?

Myasthenia Gravis Treatment

First-Line Treatment: Pyridostigmine

Start pyridostigmine immediately at 30 mg orally three times daily, titrating gradually to a maximum of 120 mg four times daily based on symptom response and tolerability. 1, 2

• Pyridostigmine is an acetylcholinesterase inhibitor that provides symptomatic relief by increasing acetylcholine availability at the neuromuscular junction 3, 2
• This may be sufficient as monotherapy in mild disease (Grade 1-2 with ocular symptoms only) 1
• Approximately 50% of patients with ocular myasthenia show minimal response to pyridostigmine alone and require escalation 3

Second-Line Treatment: Corticosteroids

Add prednisone 1-1.5 mg/kg orally daily if pyridostigmine provides insufficient control for Grade 2 symptoms (some interference with activities of daily living). 1

• Approximately 66-85% of patients show positive response to corticosteroids 3, 1
• Taper gradually based on symptom improvement 1
• Corticosteroids are the mainstay of immunosuppressive treatment for more than mild disease 4

Third-Line Treatment: Steroid-Sparing Immunosuppressants

Consider azathioprine or mycophenolate mofetil for patients requiring chronic corticosteroid therapy or those with moderate to severe disease. 3, 5

• These agents reduce long-term corticosteroid dependence and associated side effects 6, 7
• Clinical improvement may take months to years 7

Management of Myasthenic Crisis (Grade 3-4)

Immediately hospitalize patients with respiratory compromise, severe generalized weakness, dysphagia, or rapidly progressive symptoms, and initiate acute immunotherapy. 1

Crisis Protocol:

• Administer IVIG 2 g/kg IV over 5 days (0.4 g/kg/day) OR plasmapheresis for 5 days 1, 8
• Continue corticosteroids (methylprednisolone 1-2 mg/kg daily) concurrently 1
• Perform frequent pulmonary function assessments with negative inspiratory force and vital capacity monitoring 1, 8
• ICU-level monitoring with daily neurologic evaluations 8

Critical: IVIG should NOT be used for chronic maintenance therapy—reserve it only for acute exacerbations or crisis situations. 1, 8

Thymectomy Consideration

Evaluate for thymectomy in AChR antibody-positive generalized MG patients up to age 65 years. 3, 4

• 10-20% of AChR MG patients have thymoma 3
• Measure serum anti-AChR antibody levels preoperatively in any patient requiring surgery to avoid respiratory failure during anesthesia 3

Critical Medications to Avoid

Strictly educate patients to avoid medications that worsen myasthenic symptoms through neuromuscular transmission interference: 1, 8

• β-blockers 3, 1
• Intravenous magnesium 3, 1
• Fluoroquinolone antibiotics 3, 1, 8
• Aminoglycoside antibiotics 3, 1, 8
• Macrolide antibiotics 3, 1, 8
• Metoclopramide 1, 8
• Barbiturate-containing medications 1, 8

Diagnostic Confirmation Requirements

Obtain the following tests to confirm diagnosis: 1

• Acetylcholine receptor (AChR) antibodies and antistriated muscle antibodies (first-line serologic testing) 3, 1
• If AChR antibodies negative: test for muscle-specific kinase (MuSK) and lipoprotein-related protein 4 (LRP4) antibodies 1, 6
• Electrodiagnostic studies: repetitive nerve stimulation and/or single-fiber EMG with jitter studies 3, 1
• Pulmonary function testing with negative inspiratory force and vital capacity 1

Monitoring and Follow-Up

Implement vigilant monitoring as 50-80% of patients with initial ocular symptoms will develop generalized myasthenia within a few years. 3, 1

• Regular pulmonary function assessment, especially in generalized disease 3, 1, 8
• Teach patients to monitor for worsening bulbar symptoms (speech/swallowing changes), respiratory difficulties, and diplopia 1, 8
• Instruct patients to seek immediate medical attention for significant increase in muscle weakness 1, 8
• Plan regular neurology consultation to adjust treatment 1, 8

Important Clinical Pitfall

Pupils are characteristically NOT affected in myasthenia gravis—pupillary involvement should immediately prompt evaluation for third nerve palsy or other etiologies, not MG. 3, 1

• MG affects nicotinic receptors at the neuromuscular junction, not autonomic innervation responsible for pupillary function 3