Fatigue in Myasthenia Gravis typically worsens with use and improves with rest. Which option best describes this?

• A. Worsens with use and improves with rest
• B. Worsens with rest
• C. Unrelated to activity
• D. Worsens only at night

Answer: (A)

In myasthenia gravis, weakness is fatigable because transmission at the neuromuscular junction is impaired by autoantibodies to the acetylcholine receptor. With repeated use, there are fewer receptors available and the postsynaptic response to acetylcholine declines, so strength worsens as you continue to use the muscles. After a period of rest, receptor availability and acetylcholine in the synaptic cleft recover, and strength improves. This pattern—worsening with activity and improvement with rest—is the hallmark of MG. It’s why symptoms like ptosis and diplopia often fluctuate during the day and after brief rest or after acetylcholinesterase inhibitors, which increase acetylcholine at the junction, providing temporary relief.