Clinical Features and Classification of Myasthenia Gravis

Core Clinical Features

Myasthenia gravis is characterized by fatigable or fluctuating muscle weakness that typically affects proximal more than distal muscles, with ocular and bulbar involvement being common presenting features that can progress to potentially life-threatening respiratory compromise 1, 2
The American College of Neurology recommends considering myasthenia gravis in patients with fluctuating weakness, particularly if it worsens with activity and improves with rest 2
Proximal muscle involvement is a hallmark of myasthenia gravis, with weakness generally affecting proximal muscles more than distal ones 1
Bilateral presentation is common, although weakness can be asymmetrical 3

Ptosis (drooping eyelids) is often the first symptom to appear and may be unilateral or bilateral 1, 2
Diplopia (double vision) results from extraocular muscle weakness 2
Variable strabismus, slow ocular saccades, and a positive ice pack test are characteristic findings in myasthenia gravis 2

Dysarthria (slurred speech) and dysphagia (difficulty swallowing) are common bulbar manifestations of myasthenia gravis 1, 2
Facial weakness and neck weakness are also frequently observed 1, 2

Limb weakness typically affects proximal muscles more than distal ones 1
Respiratory muscle weakness can lead to respiratory insufficiency or failure, representing the most serious manifestation of myasthenia gravis 1, 2

The Myasthenia Gravis Foundation of America (MGFA) classifies myasthenia gravis into five classes based on clinical severity, with Class I being the mildest and Class V being the most severe 1, 4
Class I: Ocular MG only (ptosis, diplopia) 1, 4
Class II: Mild generalized weakness 1, 4
Class III: Moderate generalized weakness 1, 4
Class IV: Severe generalized weakness 1, 4
Class V: Myasthenic crisis requiring intubation 1, 4

Disease progression can lead to generalized MG in 50-80% of patients who initially present with ocular symptoms only 2
Myasthenic crisis is a life-threatening complication that requires ventilatory support 1, 2
Thymoma association is observed in about 10-20% of patients with AChR MG 2

Clinical examination, antibody testing, electrodiagnostic studies, pulmonary function assessment, and imaging are essential components of the diagnostic approach 1
The American Academy of Neurology recommends considering myasthenia gravis in patients with fatigable weakness and using a combination of clinical and diagnostic tests to confirm the diagnosis 1

All grades of myasthenia gravis warrant thorough evaluation due to potential for respiratory compromise 1, 4
Grade 2 (MGFA class 1-2): Consider pyridostigmine and corticosteroids if symptoms interfere with daily activities 1, 4
Grade 3-4 (MGFA class 3-4): May require hospitalization, IVIG or plasmapheresis, and higher doses of corticosteroids 1, 4
Thymectomy is considered especially if thymoma is present 2

Medications to avoid include beta-blockers, IV magnesium, fluoroquinolones, aminoglycosides, and macrolides, which can worsen myasthenia 1, 4
Atypical presentations, such as young children with nonspecific symptoms, require careful consideration of myasthenia gravis in the differential diagnosis 3
Regular assessment of respiratory function is critical to prevent life-threatening complications 2