Which autoimmune disease is associated with autoantibodies against acetylcholine receptors at the neuromuscular junction?

• A. Rheumatoid arthritis
• B. Systemic lupus erythematosus
• C. Myasthenia gravis
• D. Glomerulonephritis

Answer: (C)

Autoimmune attack on the postsynaptic nicotinic acetylcholine receptors at the neuromuscular junction disrupts transmission, reducing receptor availability and weakening the signal to muscle fibers. This leads to fatigable weakness that worsens with use and improves with rest.

This pattern is most characteristic of myasthenia gravis, where autoantibodies target acetylcholine receptors at the NMJ (often with thymic abnormalities). The immune attack decreases the end-plate potential, so muscle contraction becomes progressively harder with activity.

Rheumatoid arthritis and systemic lupus erythematosus involve different autoantibodies and primarily affect joints, skin, kidneys, and other organs rather than the neuromuscular junction. Glomerulonephritis is a kidney-focused condition that can be immune-mediated but is not driven by autoantibodies against acetylcholine receptors at the NMJ.