Autoimmune disease targets connection of nerves and muscle

Ask Dr. Keith Roach M.D

DEAR DR. ROACH: What can you tell me about myasthenia gravis? My dear friend was diagnosed with it and hospitalized for eight days. She is able to walk and move about, but now, six weeks later, she is still on a liquid diet and unable to move any of her facial muscles. — I.M. ANSWER: Myasthenia gravis, from the Latin and Greek for “serious muscle weakness,” is an autoimmune disease that attacks the connection of nerves to muscles. Specifically, the body attacks the acetylcholine receptor or its associated proteins, where nerves connect to skeletal muscles. This causes weakness of the muscles and increased susceptibility to fatigue. The diagnosis of MG is suggested by typical symptoms, the most common of which are eye symptoms like double vision or droopy eyelid (ptosis). A smaller number of people will have symptoms that involve eating and chewing — this sounds like your friend’s primary problem — and a few will have weakness in the limbs, neck or face, or of the breathing muscles. The diagnosis is usually confirmed by blood testing, but a few people will need more sophisticated testing, such as an electrical muscle stimulation test. MG commonly affects women under 40 and men over 60, but it can occur in any age group. The thymus, an immune organ that is located in the upper chest behind the sternum (breastbone), is an important origination point for MG, and 10-15% of people with MG have tumors of the thymus. Surgical removal of the thymus is often performed to improve symptoms. In addition to removal of the thymus, there are three other types of treatment for MG. The first is medicines that help the nerve-muscle receptor work better, such as pyridostigmine. This starts working within minutes. The second is treatments to get rid of the antibodies attacking the receptor. Plasmapheresis, the physical removal of antibodies, takes a few days to start working; intravenous immune globulin takes a week or two to work. It’s not clear exactly how these work in MG. The third type, anti-immune system drugs, take much longer: a few weeks for prednisone but several months at least for others, such as cyclosporine and mycophenolate. Your friend is in a period where many of the treatments have not had time to work yet, and I expect that she will get better as the treatments take hold. Her doctors may be talking to her about removing the thymus, but she needs to be well controlled before surgery. Some experts use plasmapheresis or immune globulin to get good control quickly before surgery, especially in people whose symptoms involve eating and facial functions. You can read more at www. tinyurl.com/NIHmyasthenia. *** Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYour-GoodHealth@med.cornell. edu or send mail to 628 Virginia Dr., Orlando, FL 32803.