Myasthenia gravis is best described as an autoimmune disease that attacks which target?

• A. Acetylcholine receptors.
• B. Myelin in the CNS.
• C. Presynaptic calcium channels.
• D. GABA receptors.

Answer: (A)

Myasthenia gravis is a disorder in which the immune system attacks the muscles’ communication at the neuromuscular junction. Specifically, antibodies target the nicotinic acetylcholine receptors on the postsynaptic muscle membrane. With fewer functional receptors available, the signal from acetylcholine is less likely to produce a muscle contraction, especially after repeated use. That’s why muscles get weaker with activity and improve with rest—the hallmark fatigable weakness comes from impaired transmission at the NMJ.

This contrasts with the other targets: attacking myelin in the CNS is what happens in demyelinating diseases like multiple sclerosis; antibodies against presynaptic calcium channels describe Lambert-Eaton syndrome, where neurotransmitter release is reduced from the nerve terminal; and GABA receptors involve CNS inhibition rather than the peripheral NMJ. The most characteristic feature of MG is fatigable, predominantly ocular and proximal muscle weakness due to disruption of postsynaptic acetylcholine receptor function.