FAQs about myasthenia gravis
Myasthenia gravis is a rare, debilitating form of neuromuscular disease. Here, our Division Chief of our Neuromuscular Division Vern Juel, MD, answers your questions about the condition.
What is myasthenia gravis?
Myasthenia gravis is an autoimmune disease of the neuromuscular junction. The neuromuscular junction is the special area where motor nerves communicate with muscle fibers to contract. In myasthenia gravis or MG, the immune system attacks and damages the spot on the muscle fibers where chemical messages are received from the motor nerves. This results in painless weakness that fluctuates and increases with activity and over the course of a day. The weakness typically improves with rest.
How do people get myasthenia gravis, and is it contagious?
MG is not contagious. It is an autoimmune disease like rheumatoid arthritis and lupus. We do not fully understand what causes autoimmune diseases or MG. Although most cases of MG are not inherited in a strict sense, the risk for MG appears to be increased in families where there are individuals who have MG or other autoimmune diseases. There are very rare instances of congenital myasthenia gravis in which the mechanisms for communication between motor nerves and muscle fibers are abnormal on an inherited or genetic basis. These patients develop difficulties with weakness at or shortly after birth and do not have an autoimmune disease.
Are people born with auto-immune diseases more susceptible to the disease later in life?
Yes, an individual’s risk for MG is increased if they have other autoimmune diseases.
What are its symptoms?
Patients with MG have painless weakness that fluctuates from moment to moment and increases with activity and over the course of a day. The weakness typically improves with rest. The muscles most frequently involved in MG are the eyelid muscles and the muscles that move the eyes. This results in variable eyelid drooping and in double vision due to misalignment of the eyes. The muscles of chewing, speaking, and swallowing may also be affected and produce difficulty chewing meats or candies, a slurred or nasal speech pattern, and regurgitation through the nose with attempts to swallow. Weakness of the facial muscles can result in snarling with efforts to smile. With more severe MG, patients may have difficulty holding the head erect or develop arm and/or leg weakness and difficulty breathing.
How many people have myasthenia gravis?
MG is a rare disease. About 20/100,000 people have MG, so the estimate of the number of MG patients in the Research Triangle area would be approximately 250 patients.
What does the thymus do and how is the removal of the thymus helpful in recovery?
The thymus gland is where our lymphocytes (one type of white blood cell) are thought to learn to distinguish surfaces that belong to ourselves (other cells and tissues belonging to our body) from foreign surfaces (e.g. bacteria, viruses) early in life. The thymus gland is large in infancy and early childhood while this education process is thought to be taking place. It shrinks as one matures to adulthood. Interestingly, one of the features of MG is abnormal enlargement of the thymus gland. About one in five patients with MG may have a tumor of the thymus gland called a thymoma.
How is this disease treated? How, if at all, are blood transfusions involved?
MG may be treated in several ways. Medicines (such as pyridostigmine bromide or Mestinon) that prolong the chemical messages sent by motor nerves to muscle fibers may temporarily improve strength and relieve symptoms of weakness and fatigue. Treatments that stop the immune attack on the neuromuscular junction are often necessary to improve strength and long-term immune suppressive treatments are frequently necessary to sustain the improvement. Treatments that improve MG patients most rapidly when they are critically ill include plasma exchange and intravenous immunoglobulin infusions. Plasma exchange involves processing a patient’s blood to separate the blood cells from the plasma. The plasma (containing the antibodies involved with the attack on the neuromuscular junction) is discarded, and the patient’s own blood cells are returned. Long-term immune suppression treatments include corticosteroid medicines such as prednisone along with medicines such as azathioprine and mycophenolate mofetil. These medicines are also used to prevent organ transplant rejection and to treat other autoimmune diseases. Blood transfusions are not used to treat MG.
How successful is surgery for keeping symptoms at bay?
The only role for surgery in MG is to remove the thymus gland. In MG patients without thymoma, removal of the thymus gland reduces the amount of immune suppression needed to control MG symptoms and increases the chance for drug-free MG remission. In MG patients with thymoma, removal of the thymic tumor is necessary to control the MG and to prevent displacement and invasion of important organs in the chest cavity.
What are some lifestyle changes which could help keep the disease at bay (gluten free, dairy free, carb free, exercise, low stress, etc)?
Unlike several more common diseases (e.g. type 2 diabetes mellitus, hypertension), there are no known lifestyle factors that increase or decrease one’s risk for developing MG. When MG is under good control or in remission, there are few lifestyle restrictions or limitations. Because of the fatigable quality of the muscle weakness in MG, symptomatic patients find it necessary to conserve energy and limit their exertion. Rest is important, and a full seven-to-eight hour complement of sleep is recommended. A healthy, balanced diet and exercise are recommended. Some commonly prescribed medications may increase weakness in MG patients, and these should be avoided.
How has our knowledge of myasthenia gravis changed over the past 20 years?
From a diagnostic perspective, we now recognize several subcategories of MG that are immunologically distinct with characteristic symptoms and responses to treatment. The Duke MG Clinic is working jointly with the Duke Immune Monitoring Laboratory to identify the immunology and molecular characteristics of lymphocytes in MG and how these characteristics can help guide us to select the very best treatments for MG patients. We also have collaborated with other MG investigators in the US and internationally to improve our methods of measuring MG severity and response to treatment. Future developments in MG will include development and clinical testing of increasingly targeted, specific, and effective treatments to stop the autoimmune attack on the neuromuscular junction in MG with fewer side effects.
What else can people do to help others with myasthenia gravis?