Myasthenia Gravis

As the nurse enter the examination room, she was holding a folder with the hospital’s stamp. “Ah, the lab results,” exclaimed the doctor. The neurologist turned the pages with a frown. Annie took her mother’s hand as they looked at one another. “I’m afraid I don’t have very good news. Do you remember when the nurse injected that solution into your arm and you said that suddenly you felt much stronger?” “Yes, I felt so much better, but only for a short time,” replied Annie.

“That was the edrophonium test; we injected edrophonium chloride into your vein. It temporarily relieves weakness in people who suffer from myasthenia gravis. I am afraid that the diagnosis is confirmed by these lab results, which show an abnormally high level of antibodies in your blood.”

In many cases of myasthenia gravis, the antibodies compromise communication from your nerves to your muscles. One good piece of news is that the computer tomography (CT) scan shows that there is a tumor on your thymus gland. This tumor could be the reason for your problems. The thymus can be easily removed, and this will probably decrease the symptoms; it may even cure them. Additional treatment will probably be necessary to counteract the compromised situation between your nerves and muscles, and it may have to be modified depending on the results of the thymectomy.

Questions

1. What is the role of the thymus in the body, and briefly, what are antibodies and what is an antigen?

2. Go back to the diagram and predict where the antibodies in Annie’s blood could act to decrease synaptic function at the neuromuscular junction.

3. Neostigmine is one pharmacological agent that is prescribed for people with Myasthenia Gravis. This drug, like the edrophonium chloride injection, will make Annie feel stronger. Related to the flow diagram, determine how these drugs could work to increase synaptic performance.

4. In the absence of treatment, what could happened to the amplitude of Annie’s endplate potentials...