What are the signs and symptoms of myasthenia gravis?

Signs and Symptoms of Myasthenia Gravis

Myasthenia gravis presents with fatigable or fluctuating muscle weakness that worsens with activity and improves with rest, characteristically affecting proximal more than distal muscles, with ocular and bulbar involvement being the most common presenting features. 1, 2

Cardinal Feature: Fatigability

• Fluctuating weakness that worsens with repeated muscle use and improves with rest is the hallmark of myasthenia gravis 1, 2, 3
• Symptoms vary throughout the day and worsen with physical activity or fatigue 2, 4

Ocular Manifestations (Most Common Initial Presentation)

• Ptosis (drooping eyelids) is often the first symptom, appearing unilaterally or bilaterally 1, 2, 5
• Diplopia (double vision) results from extraocular muscle weakness 1, 2, 5
• Variable strabismus that changes with fatigue or repetition of examination 1
• Extraocular movement abnormalities and ophthalmoparesis 1
• 50% of patients present with purely ocular symptoms initially, and 50-80% of these will progress to generalized myasthenia within a few years 1, 2, 5

Bulbar Manifestations

• Dysarthria (slurred speech) from facial and oropharyngeal muscle weakness 1, 2, 5
• Dysphagia (difficulty swallowing) 1, 2
• Facial muscle weakness 1, 2, 5
• Neck weakness 1, 2, 5

Limb and Proximal Muscle Weakness

• Proximal muscle weakness is more pronounced than distal weakness 1, 2, 5
• Weakness is typically more proximal than distal in distribution 1, 2
• Bilateral presentation is common, though asymmetry can occur 1, 2, 5

Respiratory Manifestations (Most Serious)

• Respiratory muscle weakness can progress to respiratory insufficiency or failure, representing a life-threatening complication 1, 2, 5
• Myasthenic crisis (MGFA Class V) requires intubation and ventilatory support 1, 2

Pattern Recognition

• Symptoms worsen with:

  • Repetitive muscle use 1, 3, 4
  • Intercurrent infections (bacterial or viral) 6
  • Fever and physical or emotional exhaustion 6
  • End of day fatigue 2

• Symptoms improve with:

  • Rest periods 1, 3, 7
  • Ice pack application (for ocular symptoms—highly specific diagnostic sign) 5

Clinical Severity Classification (MGFA)

• Class I: Ocular symptoms only (ptosis, diplopia) 1, 2, 5
• Class II: Mild generalized weakness 1, 2, 5
• Class III: Moderate generalized weakness 1, 2, 5
• Class IV: Severe generalized weakness 1, 2, 5
• Class V: Myasthenic crisis requiring intubation 1, 2, 5

Critical Pitfalls to Recognize

• Myasthenia is known as "the great masquerader" because presentation can mimic many types of incomitant strabismus with or without ptosis 1
• The pattern of weakness may change entirely with fatigue or repetition of examination 1
• All grades warrant immediate work-up due to potential for progression to respiratory compromise 1, 2
• May occur concurrently with myositis and/or myocarditis, particularly in immune checkpoint inhibitor-associated cases 1