Myasthenia gravis is an autoimmune neuromuscular disorder causing weakness and fatigability of skeletal muscle that worsens with continued use.
Etiology and Pathogenesis
Myasthenia gravis results from a fall in AChR number at the motor end plate, caused by circulating autoantibodies against the receptor.
Anti-AChR antibodies act by three mechanisms: receptor blockade (competing with ACh for AChR), antibody-induced AChR endocytosis, and damage to the postsynaptic membrane.
Postsynaptic folds become flattened (simplified); ACh is released normally, but the resulting end plate potential falls below threshold for a muscle action potential.