Myasthenia gravis targets muscle, nerve connections

Dr. Keith Roach

Question: What can you tell me about myasthenia gravis? I’d like to know how it’s contracted, and what the treatment options are.

— Y.H.

Answer: Myasthenia gravis is a disease of the connection between nerve and muscle. It is caused by an autoimmune process — meaning, the body mistakenly destroys one of the nerve/muscle receptors, which is how the nerve communicates information from the brain to the muscle. The most common receptor is the acetylcholine receptor, but a smaller number of people with MG have antibodies to a different receptor, the muscle-specific tyrosine kinase. The thymus, an obscure organ in the neck (and the “T” of T-cells), may be the source of the autoimmune reaction.

The symptoms of MG are weakness and easily fatigued muscles, especially the muscles of the eye, which is where symptoms usually start. The muscle weakness comes and goes, and often people (or their friends) notice a drooping eyelid on one or both sides. Double vision is a common symptom.

There are many treatment options. Initially, many people with MG will be prescribed medication such as pyridostigmine (Mestinon). This keeps the acetylcholine in the synapse (the connection between the nerve and muscle) longer. In some people, it provides a dramatic benefit.

Medications used for other autoimmune diseases also are used in MG. These agents — such as steroids, azathioprine and cyclosporine — suppress the immune system and reduce the destruction of the receptors, but increase the likelihood of infection. The antibodies can be removed with plasmapheresis, but the benefits last only a few weeks; this therapy is used for crises and if surgery is needed.

Finally, surgical removal of the thymus gland can improve symptoms and reduce medication need.

Q: I am a 77-year-old man in good health. I take 7.5 mg amlodipine a day for hypertension. Since taking the medication, I have developed annoying lower-leg swelling. Are you aware of any adverse consequences from the edema associated with this medication?

— L.B.

A: Amlodipine, like similar calcium channel blockers, works by relaxing blood vessels. This reduces pressure, but it can allow fluid to leak out of the vessels. The fluid tends to be pulled down to the feet by gravity. People worry about it because foot swelling can be a sign of serious liver, kidney or heart disease. However, the swelling from amlodipine usually is just annoying, and can be managed by raising the feet periodically or wearing compression stockings. Rarely, people can develop chronic skin changes.