Which of the following is a prominent characteristic of Myasthenia Gravis?

Myasthenia Gravis is primarily characterized by muscle weakness that worsens with activity and tends to improve with rest. This condition is caused by an autoimmune response where antibodies disrupt communication between nerves and muscles at the neuromuscular junction. As patients engage in prolonged or repetitive muscle activity, the synaptic transmission becomes less effective, leading to increased weakness. Therefore, the worsening of muscle strength throughout the day aligns perfectly with this condition's typical presentation.

In contrast, improved muscle strength with activity is more characteristic of certain other neuromuscular disorders, where initial exertion can lead to temporary enhancement before fatigue sets in. Muscle rigidity and stiffness are more associated with conditions like Parkinson's disease or other movement disorders rather than Myasthenia Gravis. Similarly, muscle spasms are not a defining symptom of this disease; spasms are usually indicative of different underlying conditions. Understanding these nuances is key in differentiating Myasthenia Gravis from other muscular disorders.