A 31-year-old, otherwise healthy female presents to the emergency room with 2 days of progressive shortness of breath and difficulty swallowing. She reports over the past year that she gets tired much more easily through the day, to the point where it is difficult to keep her eyes open or head up, but this improves with rest. Recently she developed difficulty chewing solid foods, primarily at dinner. Her vision gets blurry at the end of the day, and she sometimes sees two of the same object when both her eyes are open.