Myasthenia gravis is an autoimmune disease primarily affecting striated muscles. It most commonly occurs between the ages of 20 and 40, with a higher prevalence in females, though it can also affect infants and children. Ocular involvement is observed in 90% of cases, with 80%–90% of adult patients presenting with ptosis and diplopia as initial symptoms. These symptoms typically exhibit a characteristic pattern of improvement in the morning and worsening by evening. Due to the variable involvement of extraocular muscles, asymmetry between the two eyes is often noted, and in severe cases, the eyes may become fixed and immobile.
The diagnosis is based on the following criteria: (1) Muscle weakness of the affected muscles shows improvement in the morning, worsening with fatigue, and relief after rest. (2) Repeated movement of the affected muscles, such as closing and opening the eyes, may result in temporary paralysis. (3) Intramuscular injection of 0.5–1.0 mg of neostigmine leads to significant symptom relief within 15–30 minutes. (4) Chest CT may reveal the presence of a thymoma.