A client asks what causes myasthenia gravis. Which description of pathology would the nurse use in response to the client?

A client asks what causes myasthenia gravis. Which description of pathology would the nurse use in response to the client?

• A. A decreased number of functioning acetylcholine receptor (AChR) sites
• B. A genetic defect in the production of acetylcholine (ACh)
• C. An inefficient use of the neurotransmitter ACh
• D. An inhibition of the enzyme acetylcholinesterase (AChE), leaving the end plates folded

Answer: (A)

The main idea is that myasthenia gravis is an autoimmune attack that reduces the number of functional acetylcholine receptors on the postsynaptic muscle membrane at the neuromuscular junction. When acetylcholine is released, there are fewer receptors available to respond, so the signal often fails to produce a strong enough end-plate potential to trigger a muscle contraction. This loss of receptor sites leads to the characteristic fatigable weakness that worsens with activity and improves with rest or with acetylcholinesterase inhibitors, which help by increasing acetylcholine presence at the junction. The other descriptions don’t fit MG as well. It isn’t a genetic defect in acetylcholine production, because acetylcholine release is not the primary problem—receptor availability is. It isn’t about inefficient use of the transmitter; the issue isn’t that acetylcholine is used poorly, but rather that there aren’t enough receptors to respond to it. Inhibition of acetylcholinesterase would raise acetylcholine levels and is used as a treatment to improve transmission, not a description of the disease’s cause, and the notion of end plates being folded isn’t the pathogenic mechanism in MG.

The main idea is that myasthenia gravis is an autoimmune attack that reduces the number of functional acetylcholine receptors on the postsynaptic muscle membrane at the neuromuscular junction. When acetylcholine is released, there are fewer receptors available to respond, so the signal often fails to produce a strong enough end-plate potential to trigger a muscle contraction. This loss of receptor sites leads to the characteristic fatigable weakness that worsens with activity and improves with rest or with acetylcholinesterase inhibitors, which help by increasing acetylcholine presence at the junction.

The other descriptions don’t fit MG as well. It isn’t a genetic defect in acetylcholine production, because acetylcholine release is not the primary problem—receptor availability is. It isn’t about inefficient use of the transmitter; the issue isn’t that acetylcholine is used poorly, but rather that there aren’t enough receptors to respond to it. Inhibition of acetylcholinesterase would raise acetylcholine levels and is used as a treatment to improve transmission, not a description of the disease’s cause, and the notion of end plates being folded isn’t the pathogenic mechanism in MG.