Myasthenia gravis is characterized by fluctuating and fatigue-prone muscle weakness in certain specific striated muscles. Symptoms are generally milder in the morning and more severe in the evening, worsening with continued activity and alleviating after rest.

The most common initial symptom is weakness of the external eye muscles, primarily presenting as asymmetrical ptosis (drooping of the upper eyelid) or narrowing of the eye slit, along with diplopia, which refers to seeing double images. These are the most frequent initial symptoms, seen in over 50% of patients with myasthenia gravis.

Additionally, some patients may experience disturbances in eye movement, facial muscle weakness, air leakage when puffing cheeks, incomplete eyelid closure, shallower nasolabial folds, as well as difficulty swallowing, speech articulation issues, choking while drinking, and potentially severe respiratory weakness.