Myasthenia gravis

Myasthenia gravis is a chronic autoimmune disorder in which antibodies impair signaling at neuromuscular junctions, causing fluctuating skeletal-muscle weakness that often worsens with activity.

Neuromuscular junction: The synapse where a motor neuron communicates with a skeletal muscle fiber. This is the site where myasthenia gravis antibodies impair nerve-to-muscle signaling.
Edrophonium test: A historical diagnostic test that briefly inhibits acetylcholinesterase to assess muscle strength. It once tested for transient improvement, but is now rarely used because of risks and limitations.
Autoimmunity: An immune response directed against the body's own cells or molecules. Myasthenia gravis begins when immune defenses target proteins at the neuromuscular junction.
Lambert–Eaton myasthenic syndrome: An autoimmune disorder in which antibodies impair presynaptic calcium channels, reducing acetylcholine release. It also causes fatigable weakness, but the immune target lies on the nerve side of the junction.
Acetylcholine receptor: A membrane protein that binds acetylcholine and helps trigger muscle contraction. Antibodies against this receptor cause the most common form of myasthenia gravis.
Pyridostigmine: A reversible acetylcholinesterase inhibitor used to increase acetylcholine at neuromuscular junctions. It commonly provides symptomatic relief by prolonging acetylcholine’s action.
Antibody: A protein made by B cells that binds a specific molecular target. Disease-causing antibodies bind junction proteins and interfere with their function.
Congenital myasthenic syndrome: A group of inherited disorders that impair neuromuscular transmission without an autoimmune cause. Similar weakness can occur, but it results from genetic defects rather than pathogenic antibodies.
Muscle-specific kinase: A protein that organizes acetylcholine receptors at the neuromuscular junction. Antibodies against MuSK disrupt receptor organization and produce a distinct disease subtype.
Thymectomy: Surgical removal of the thymus gland. It is considered for thymoma and can improve outcomes in selected patients without thymoma.

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