Myasthenia Gravis, rare and hard to diagnose
| June 9, 2021 1:00 AM
It only occurs in 14 to 40 per 100,000 people in the United States. However, reports indicate that the frequency of myasthenia gravis (MG) is increasing. It could be because it's reported more often, or it could be because studies have shown that the rate of all autoimmune diseases is rising.
Affecting more women than men, MG symptom onset typically occurs in women in their 20s or 30s and men in their 50s and 60s. But, it can strike at any age. James Carter was diagnosed with MG when he was 12. He was unable to run, walk or even chew his food. Wikipedia says, "He soon had surgery to have a tumor removed from his chest, and he was able to return to the sport of track and field …" He's now an Olympic gold medalist.
The tumor, most likely, was in his thymus gland, a part of the body's immune system. This gland is large in infants but decreases in size as we mature. People with MG often have an abnormally large thymus gland that can cause tumors called thymomas.
But I've gotten ahead of myself. What is myasthenia gravis? Mayo Clinic describes it as a disease characterized by weakness and rapid fatigue of any muscles under your voluntary control.
"Your nerves communicate with your muscles by releasing chemicals (neurotransmitters) that fit precisely into receptor sites on the muscle cells at the nerve-muscular junction. In myasthenia gravis, your immune system produces antibodies that block or destroy many of your muscles' receptor sites for a neurotransmitter called acetylcholine. With fewer receptor sites available, your muscles receive fewer nerve signals, resulting in weakness." Mayo explains.
"Muscle weakness caused by MG worsens as the affected muscle is used. Because symptoms usually improve with rest, muscle weakness can come and go. However, the symptoms tend to progress over time, usually reaching their worst within a few years after the onset of the disease," they say.
The signature symptoms involve eye problems. More than half of people with MG will experience drooping of one or both eyelids and double vision (diplopia). Diplopia may be horizontal or vertical and improves when one eye is closed.
"In about 15 percent of people with myasthenia gravis, the first symptoms involve face and throat muscles, which can impair speaking, cause difficulties swallowing, affect chewing and change facial expressions," Mayo says.
A woman named Maria, who was the headteacher at a school in England, described her symptoms to My Aware, an organization fighting myasthenia gravis: "As I was about to do a Bible reading in front of the whole school, I began to slur my speech. I sounded as though I was drunk. I just managed to sit down and ask someone else to do the reading when my head dropped onto my chest, and I couldn't lift it. Pretending to find my shoes especially interesting, I resolved to get an urgent appointment with the neurologist. A few minutes later, I was fine and left the school hall under my own steam, telling everyone, not to fuss."
The National Organization for Rare Diseases says that "myasthenia gravis is diagnosed based upon a thorough clinical evaluation, detection of characteristic symptoms and physical findings, a detailed patient history, and a variety of specialized tests."
One test involves the healthcare provider putting an ice pack on the droopy eyelid. After a couple of minutes, the ice pack is removed, and the eye is checked for signs of improvement. In another test, the clinician attaches electrodes to the skin over affected muscles. Then a small pulse of electricity is administered through the electrode to measure the nerve's ability to send a signal to the muscle.
Other tests include blood analysis and diagnostic imaging, including a CT scan or an MRI. The medico may also do a pulmonary function test to evaluate the diseases' effect on breathing.
As is typical for autoimmune diseases, there is no cure. Treatment is aimed at relieving symptoms. "Your treatment will depend on your age, how severe your disease is and how fast it's progressing," Mayo says. Initial treatment is typically medications to increase muscle strength and immunosuppressive drugs to alter the disease's course. Surgery is a last resort.
Kathy Hubbard is a member of the Bonner General Health Foundation Advisory Council. She can be reached at firstname.lastname@example.org.