myasthenia gravis

Chronic autoimmune disease causing muscle weakness. Autoantibodies block the response of muscle cells to acetylcholine. Muscles weaken with repeated use but regain their strength after rest. The pattern varies, but usually muscles used in eye movements, facial expressions, chewing, swallowing, and respiration are affected first, then neck, trunk, and limb muscles. Severe cases impede breathing. Anticholinesterase drugs stimulate nerve-impulse transmission, and corticosteroids may help. Removal of the thymus has improved severe cases. Remission lasting several years may occur.

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• Myasthenia gravis
• Ocular myasthenia
• Lambert-Eaton myasthenic syndrome