Muscle Weakness and Double Vision

🗒️ Question

A 27 year old woman presents with episodes of muscle weakness that worsen with activity and improve with rest. She also reports double vision and difficulty swallowing towards the end of the day. Her symptoms have been progressively worsening over the past few months. She has no significant medical history.

On examination, her cranial nerve examination shows bilateral ptosis which worsens with sustained upward gaze. There is mild facial muscle weakness, however her limb strength is otherwise normal.

Investigations

• Serum acetylcholine receptor antibodies: Positive

• Chest X-ray: Normal

What is the most likely diagnosis?

(A) Amyotrophic lateral sclerosis

(B) Lambert-Eaton myasthenic syndrome

(C) Multiple sclerosis

(D) Myasthenia gravis

(E) Polymyositis