Symptoms of Myasthenia Gravis
Myasthenia gravis presents with fluctuating muscle weakness that worsens with activity and improves with rest, most commonly starting with ocular symptoms (ptosis and diplopia) before potentially progressing to life-threatening generalized weakness affecting bulbar, limb, and respiratory muscles. 1, 2
Ocular Symptoms (Most Common Initial Presentation)
Ocular symptoms are the first to appear in 50% of myasthenia gravis patients and include: 1
- Ptosis (drooping eyelids) - may be unilateral or bilateral, often asymmetric 3, 2
- Diplopia (double vision) - results from extraocular muscle weakness 3, 1
- Variable strabismus - misalignment of the eyes that changes during prolonged examination 3, 1
- Slow saccades - impaired rapid eye movements 3, 2
The ocular muscles are particularly susceptible because of their twitch fiber composition and fewer acetylcholine receptors. 1 A critical pitfall: 50-80% of patients with initial ocular-only symptoms will progress to generalized myasthenia within a few years, making early recognition essential. 1, 2
Bulbar Symptoms
When the disease affects bulbar muscles, patients experience: 2
- Difficulty chewing - weakness of masticatory muscles 3, 1
- Dysphagia (difficulty swallowing) - can lead to aspiration risk 3, 2
- Slurred speech (dysarthria) - speech becomes progressively unclear with talking 3, 2
- Facial weakness - affects facial expression 2
Generalized Muscle Weakness
Proximal muscles are affected more than distal muscles, with characteristic features including: 2
- Difficulty holding up the head - neck extensor weakness 3, 1
- Limb weakness - predominantly proximal (shoulders, hips) rather than distal 2
- Variable motor weakness - affecting different muscle groups 3
Respiratory Symptoms (Most Serious)
Respiratory muscle weakness represents the most life-threatening manifestation and includes: 1, 2
- Respiratory fatigue - progressive difficulty breathing 3, 1
- Respiratory insufficiency or failure - may require ventilatory support (myasthenic crisis, MGFA Class V) 1, 2
Characteristic Temporal Pattern
The hallmark features that distinguish myasthenia gravis from other neuromuscular disorders are: 1
- Fluctuating weakness - symptoms vary throughout the day and during examination 3, 1
- Fatiguability - worsening with continued activity or repetitive use of affected muscles 1, 4
- Improvement with rest - temporary symptom relief after resting 1, 4
- Worsening as day progresses - symptoms typically worse in evening 1
Important Clinical Caveats
Pupils are typically NOT affected in myasthenia gravis, though rare cases may show impaired responses. 3 Pupillary involvement should alert you to consider alternative diagnoses such as third nerve palsy. 3
The disease is considered a "great masquerader" because it can mimic many types of eye movement disorders, making clinical suspicion essential. 1 The variable presentation means the pattern of weakness can change even during a single examination. 1
Symptoms worsen with intercurrent infection, fever, and physical or emotional exhaustion, with respiratory infection being the most frequent trigger. 5