Books, Journals, New Media Section Editor: Harriet
S. Meyer, MD, Contributing Editor, JAMA; David H. Morse, MS, University
of Southern California, Norris Medical Library, Journal Review Editor; adviser
for new media, Robert Hogan, MD, San Diego.
Myasthenia gravis (MG) is the most thoroughly understood autoimmune
disease. The target antigen is the skeletal muscle nicotinic acetylcholine
receptor. The disease is clearly caused by antibodies directed at the acetylcholine
receptor. The autoimmune attack directed at the acetylcholine receptors damages
the endplate membrane where the acetylcholine receptors are concentrated.
Acetylcholine receptors and other critical membrane proteins, such as voltage-gated
sodium channels, are lost from the endplate membrane, which compromises neuromuscular
transmission. The endplate membrane becomes less sensitive to acetylcholine
released by the motor nerve terminal, and the excitability of the endplate
membrane is reduced. Weakness develops when activation of the nerve terminal
no longer stimulates action potentials in the muscle fiber. The autoimmune
nature of MG is reinforced by several observations. Inducing an allergic reaction
to the acetylcholine receptor is the basis for one animal model of MG. Serum
from patients with myasthenia can produce MG when injected into appropriate
animals. The disease is treated by interventions that attenuate the immune
response or enhance neuromuscular transmission.
Ruff RL. Myasthenia Gravis. JAMA. 2003;289(6):758-759. doi:10.1001/jama.289.6.758