What best describes the characteristic course of myasthenia gravis?

• A. Increased reflexes with muscle rigidity.
• B. Tremor with movement.
• C. Progressive muscle weakness that improves with rest.
• D. Spastic paralysis.

Answer: (C)

Fatigable weakness that worsens with use and improves with rest is the hallmark of myasthenia gravis. This autoimmune condition targets nicotinic acetylcholine receptors at the neuromuscular junction, reducing functional receptor numbers and impairing signal transmission. With repeated or sustained activity, transmission becomes increasingly insufficient, so muscles become weaker. After a period of rest, acetylcholine can interact with the remaining receptors again, briefly restoring strength. Clinically this often begins with ocular or bulbar involvement and then proximal limb weakness, showing fluctuation and diurnal variation. This pattern distinguishes it from conditions with constant high tone or reflex changes, such as spastic or rigid disorders. Treatments that boost neuromuscular transmission or modulate the immune system help lessen the fatigable weakness.