Clinical Manifestations of Myasthenia Gravis

Primary Muscle Groups Affected

Myasthenia gravis (MG) causes fatigable or fluctuating muscle weakness that typically affects proximal muscles more than distal muscles, with common involvement of ocular, bulbar, and respiratory muscles 1, 2
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 1
Variable strabismus (misalignment of eyes) is characteristic 1
Extraocular muscles are particularly susceptible to fatigue due to their twitch fiber composition and fewer acetylcholine receptors 1
Dysarthria (slurred speech) is common 2
Dysphagia (difficulty swallowing) affects many patients 2
Facial muscle weakness causes reduced facial expressions 1, 2
Neck weakness may lead to difficulty holding up the head 1
Proximal limb muscles are affected more than distal muscles 2
Weakness is typically bilateral but can be asymmetrical 2
Trunk muscles may be involved, affecting posture 1
Respiratory muscle weakness represents the most serious manifestation 1, 2
Can progress to respiratory insufficiency or failure (myasthenic crisis) 1
Requires close monitoring of pulmonary function 3

50% of patients initially present with ocular symptoms only 1
Classified as MGFA Class I when limited to ocular muscles 2
50-80% of those with initial ocular symptoms develop generalized MG within a few years 1
Progression typically follows a pattern from ocular to bulbar to limb to respiratory involvement 2
Classified as MGFA Classes II-V based on severity 2

Fluctuating weakness is the hallmark feature, with symptoms worsening with continued activity and improving with rest 1, 2
Fatiguability is characteristic, with symptoms worsening as the day progresses 1
Variable presentation during examination is typical 1
Temporary improvement with rest or application of ice (ice pack test) is characteristic 1

AChR antibodies are found in nearly all patients with generalized MG and 40-77% with ocular MG 1
Pulmonary function assessment with negative inspiratory force (NIF) and vital capacity (VC) is essential 3
Electrodiagnostic studies show characteristic neuromuscular junction dysfunction 2, 3

Failure to recognize respiratory compromise, which can rapidly progress to life-threatening myasthenic crisis 1, 3
Certain medications can worsen MG symptoms, including beta-blockers, IV magnesium, fluoroquinolones, aminoglycosides, and macrolide antibiotics 2, 3