29th April 2024

A 50-year-old woman presents with a 6-month history of progressive muscle weakness, especially towards the end of the day.

A 50-year-old woman presents with a 6-month history of progressive muscle weakness, especially towards the end of the day. She reports difficulty keeping her eyes open, double vision, and slurred speech by the evening. Her symptoms improve after resting. Physical examination reveals ptosis and diplopia, which worsen with prolonged upward gaze. Muscle strength is normal in the morning but decreases with repeated activity. There are no sensory deficits or reflex abnormalities.

Which is the most likely diagnosis?