What is myasthenia gravis?
Myasthenia gravis is a neurological condition characterized by weakness of the skeletal muscles. In myasthenia gravis, only the muscles used for movement (not involuntary muscles such as the heart) are affected. Myasthenia gravis arises because the body’s own immune system attacks the point at which the nerves signal the muscles to move. Over time, the nerves lose their ability to stimulate muscles.
Myasthenia gravis is a result of impaired communication between nerves and muscles. In particular, in myasthenia gravis, the body makes antibodies (autoantibodies) that block the receptors for an important neurotransmitter chemical at the point where nerves join muscles. As with many other autoimmune disorders, you are more likely to get myasthenia gravis if you have other autoimmune conditions. A significant number of individuals diagnosed with myasthenia gravis have an abnormal growth in their thymus, a lymphoid organ that processes immune-regulating cells.
Symptoms of myasthenia gravis, in addition to muscle weakness, include difficulty breathing, difficulty eating, eyelid droop, facial paralysis, fatigue, and difficulty with vision. Most of these symptoms worsen with physical activity. While these symptoms generally can be controlled, in some cases a myasthenic attack can occur. These attacks impair the function of breathing muscles and can be life threatening if not immediately treated.
There is no cure for myasthenia gravis, but it can be treated. Certain lifestyle factors can be changed to improve symptoms, such as decreasing physical activities and avoiding stress. Medications for myasthenia gravis include drugs to help with nerve signaling and suppress the autoimmune response. In some situations, plasmapheresis (a blood purification process) or an immunoglobulin infusion (infusion of helpful antibodies) can be used to alleviate symptoms. In patients with severe symptoms, surgery may be required to remove all or part of the thymus, an organ that is important in the development of immune system cells. In many cases, these treatments can cause myasthenia gravis to go into remission.
Seek immediate medical care (call 911) for serious symptoms of a myasthenic attack such as severe difficulty breathing. Myasthenic attacks can be life threatening.
Seek prompt medical care for any symptoms of myasthenia gravis, as this is a serious condition which can be alleviated with medical treatment.
What are the symptoms of myasthenia gravis?
Symptoms of myasthenia gravis mainly include muscle weakness, specifically of the voluntary muscles. This includes weakness in the muscles of the eye, which can lead to vision difficulties. Muscle weakness can also affect muscles involved with breathing, which can cause breathing difficulties. The symptoms of myasthenia gravis generally worsen with physical activity. In very serious cases, symptoms can progress to a myasthenic attack, in which breathing difficulty can become life threatening.
Common symptoms of myasthenia gravis
You may experience myasthenia gravis symptoms daily or just once in a while. At times any of these symptoms can be severe:
- Blurred or double vision
- Difficulty breathing
- Difficulty eating
- Difficulty engaging in physical activity
- Difficulty talking
- Drooping eyelids
- Drooping head
- Eye muscle weakness
- Facial paralysis
- Muscle weakness
Serious symptoms that might indicate a life-threatening condition
In some cases, myasthenia gravis can be life threatening. In case of a myasthenic crisis, ventilation in a hospital setting is necessary. Seek immediate medical care (call 911) if you, or someone you are with, have any life-threatening symptoms, including respiratory or breathing problems, such as shortness of breath, difficulty breathing or inability to breathe, labored breathing, wheezing, or choking.
What causes myasthenia gravis?
Myasthenia gravis is not passed down in families, nor is it contagious. Myasthenia gravis occurs when the immune system attacks acetylcholine receptors (important binding sites for the chemical involved in signaling from nerves to muscles), which are components of the neuromuscular junction (the point where nerves join muscles). When the neuromuscular junction stops functioning, signals from the nerve are not properly transmitted to the muscle. This leads to muscle weakness because the muscle does not contract when it is supposed to contract.
It is unclear why the immune system attacks acetylcholine receptors in myasthenia gravis, but it likely represent a biologic case of mistaken identity. As in many other autoimmune disorders, the body begins to attack itself inappropriately, which researchers think might be due a problem with the thymus, an organ in the chest that makes immune cells. For reasons not yet known, the thymus appears to train immune cells to make antibodies to the acetylcholine receptor. Currently, much research is aimed at understanding the role that the thymus plays in the development of myasthenia gravis.
A number of factors increase the risk of developing myasthenia gravis. Not all people with risk factors will get myasthenia gravis. Risk factors for myasthenia gravis include:
- Female gender and age under 40 years
- Male gender and age over 60 years
- Other autoimmune disorders
How is myasthenia gravis treated?
While there is no cure for myasthenia gravis, it can be treated with lifestyle modifications, medication, and, in some cases, surgery. In many cases, myasthenia gravis can go into remission (period of time without symptoms) with treatment. It is possible for people with myasthenia gravis to lead normal lives, including having children, so long as appropriate medical monitoring and treatment are obtained.
Lifestyle modifications for myasthenia gravis
The muscle weakness that occurs with myasthenia gravis is generally worsened by physical activity. Furthermore, vision problems can occur due to weak eye muscles. To address these symptoms, certain lifestyle modifications can be helpful including:
Eye patches for double vision
Lens prisms to improve vision
Scheduled physical activity with regular rest
Medications for myasthenia gravis
Drug therapy for myasthenia gravis attempts to improve the function of the acetylcholine receptors, which are key components of the junction between nerves and muscles, and to suppress the autoimmune attacks on acetylcholine receptors. Such medications include:
Anticholinesterase agents, such as neostigmine (Prostigmin, Vagostigmin) and pyridostigmine (Mestinon), to improve nerve impulse transmission
Immunosuppressants, such as azathioprine (Azasan and Imuran), cyclosporine (Gengraf and Sandimmune), mycophenolate mofetil (CellCept), prednisone (Deltasone and Orasone) and tacrolimus (Prograf), to reduce immune system attacks on acetylcholine receptors
Other treatments for myasthenia gravis
In serious cases, it may be necessary to use more invasive means to treat myasthenia gravis including:
Immunoglobulin infusion (an infusion of helpful antibodies) to dilute autoimmune antibodies
Plasmapheresis (a blood purification procedure) to remove antibodies attacking acetylcholine receptors from the blood
Surgery on the thymus to prevent the production of antibodies
Ventilation (breathing machine) in cases of a myasthenic crisis. Ventilation may be combined with plasmapheresis to treat crises.
What you can do to improve your myasthenia gravis
In addition to planning and reducing physical activity, you may be able to improve your symptoms of myasthenia gravis by:
Avoiding excessive sun exposure
Reducing your exposure to infection (good hygiene, handwashing, avoid close contact with infected individuals)
Long-term remission of myasthenia gravis is possible with treatment. However, myasthenia is a serious condition that can lead to serious complications. Complications of untreated or poorly controlled myasthenia gravis can be life threatening in some cases. You can help minimize your risk of serious complications by following the treatment plan you and your health care professional design specifically for you. Complications of myasthenia gravis include: