What is the pathophysiology and common treatment for myasthenia gravis?

• A. Degenerative loss of dopamine neurons; levodopa
• B. Autoimmune attack on acetylcholine receptors at NMJ; acetylcholinesterase inhibitors and immunosuppression; thymectomy considered in thymoma
• C. Demyelination of the CNS
• D. Neurodegeneration with tau protein; acetylcholinesterase inhibitors only

Answer: (B)

Myasthenia gravis is an autoimmune disorder in which antibodies target postsynaptic acetylcholine receptors at the neuromuscular junction. This reduces receptor numbers and impairs signal transmission, so muscles tire with use and strength improves after rest.

The best treatment approach combines strategies that improve transmission and reduce the autoimmune attack. Acetylcholinesterase inhibitors, such as pyridostigmine, increase acetylcholine availability at the junction, helping maintain muscle contraction. Immunosuppressive therapy (steroids or other immunosuppressants) lowers antibody production and autoimmune activity. If a thymic abnormality is present, thymectomy is considered because the thymus often contributes to the disease process. In more urgent or severe weakness, plasmapheresis or IV immunoglobulin can rapidly remove or neutralize circulating antibodies to provide quick improvement.

Other choices describe different diseases (for example, Parkinson disease with loss of dopamine, multiple sclerosis with CNS demyelination, or Alzheimer-type neurodegeneration with tau) and do not reflect the mechanism or treatment of myasthenia gravis.