Myasthenia gravis is a relatively rare neuromuscular disease in which the voluntary muscles easily become tired and weak because there is a problem with how the nerves stimulate the contraction of muscles. It is an autoimmune disorder.
“Myasthenia gravis” literally means “grave muscle weakness,” but many cases are mild, and life expectancy is normal.
The muscles around the eyes tend to be affected first, causing the eyelids to droop. Patients may experience double vision, weakness in the arms and legs, and difficulties chewing, swallowing, speaking, and breathing. Involuntary muscles, such as the heart muscles, are not affected.
Symptoms often worsen with physical activity and improve after resting or a good night’s sleep. There is no cure, but treatment can relieve and even remove symptoms.
The condition affects 14 to 20 people in every 100,000 in the United States, or between 36,000 and 60,000 people. It can happen at any age, but it is more likely to affect women before the age of 40 years, and men after the age of 60 years.
With myasthenia gravis, the limbs can weaken.
There is no cure for myasthenia gravis, but treatment with immunosuppressants or cholinesterase inhibitors can help control symptoms.
Many patients find that with treatment, and adequate sleep and rest, they can carry on with their normal routine.
Cholinesterase inhibitors: These improve communication between nerves and muscles, and are effective in patients with mild symptoms of MG.
Steroids, such as prednisolone, or immunosuppressants, such as azathioprine, may alter the body’s immune system so that it produces fewer of the antibodies that cause MG.
It usually takes about 4 weeks for steroids to take effect. Azathioprine may take from 3 to 6 months, but it brings about a significant reduction or complete removal of symptoms.
In the case of a tumor, the thymus gland may be surgically removed in a thymectomy.
For patients with severe or life-threatening symptoms, plasmapheresis and immunoglobulin therapy can be administered in the hospital.
Plasmapheresis involves depleting the body of blood plasma without depleting the body of its blood cells, in order to remove the unwanted antibodies.
Intravenous immunoglobulin therapy involves injecting the patient with normal antibodies that change the way the immune system acts.
These treatments are effective, and they work quickly, but the benefits last only a few weeks, so this is a short-term treatment.
Symptoms of myasthenia gravis (MG) vary widely. In some people, only the eye muscles will be affected, while in others, it can impact many muscles, including those that control breathing.
The most prevalent symptom is fatigue.
Drooping in one or both eyelids, double vision, or both are an early sign in 2 out of every 3 patients. This can cause eyesight problems, and it is known as ocular myasthenia gravis.
In 1 in 6 patients, the throat and face muscles are the first to be affected.
They may have problems with:
Speaking: Speech may become soft or nasal.
Swallowing: The person may choke easily, and eating, drinking, and swallowing pills becomes harder. When the person drinks, liquid may come out of the nose.
Chewing: The muscles used for chewing may weaken during a meal, especially if the food is hard or chewy, such as a steak.
Facial expressions: A different or unusual smile may develop if certain facial muscles are affected.
Limb weakness is the first sign in 10 percent of patients. The arm and leg muscles may weaken, affecting activities such as lifting or walking.
When limb muscles are involved, other muscles also tend to be affected, such as the throat, eyes, or face.
Symptoms often become progressively worse during periods of activity, but they improve after resting.
What is a myasthenic crisis?
A myasthenic crisis is when the respiratory muscles become paralyzed.
The patient needs assisted ventilation to stay alive.
If a patient already has weakened respiratory muscles, a myasthenic crisis may be triggered by infection, fever, an adverse reaction to some medication, or emotional stress.
In a myasthenic crisis, the respiratory muscles become so weak that the patient cannot breathe properly.
This potentially life-threatening complication requires emergency treatment with mechanical breathing assistance. Plasmapheresis and immunoglobulin therapies can help.
People with one autoimmune disease are often susceptible to another. A person with MG may have a second autoimmune condition.