What is Myasthenia Gravis? Symptoms & Treatment

Myasthenia gravis is an autoimmune disease and neuromuscular disorder that affects approximately 20 people out of every 100,000. Experts estimate that some 36,000 to 60,000 people in the United States are living with myasthenia gravis (MG). However, the number could be higher because many people with a mild form of the condition may not know they have it. Please continue reading to learn more about myasthenia gravis causes, risk factors, symptoms, diagnosis, and treatments.

What is the main cause of myasthenia gravis?

Myasthenia gravis belongs to a group of disorders called autoimmune disorders. In people with myasthenia gravis and other autoimmune diseases, the body’s immune system mistakenly attacks healthy tissues.

Specifically, in autoimmune myasthenia gravis, the immune system attacks the neuromuscular junctions, where nerves and muscles communicate through sites called acetylcholine receptors.

In healthy people, the nerve-muscle communication at the neuromuscular junction works like this: Nerve endings release a neurotransmitter called acetylcholine, which binds to an acetylcholine receptor on the muscle cells, like a hand fitting into a glove. This binding of acetylcholine to a receptor triggers a muscle contraction.

In people with myasthenia gravis, the immune system forms acetylcholine receptor antibodies that attack the neuromuscular junction and prevent normal communication between nerve cells and muscle fibers.

What are the risk factors for myasthenia gravis?

Myasthenia gravis is most common in women between 20 and 40 years of age and men between 50 and 80 years of age. Approximately 10% of cases occur in adolescents (this is called juvenile myasthenia gravis).

Other known risk factors for myasthenia gravis include:

A history of another autoimmune disorder, such as lupus or rheumatoid arthritis.
Infections (no specific bacteria or virus has been linked to myasthenia gravis, however).
Thymus gland hyperplasia and thymus gland tumors, called thymomas.
Thyroid disease.
Surgical procedures.
Myasthenia gravis worsens after taking certain medications such as antimalarials, certain antibiotics, medications used to treat heart rhythm irregularities, cancer drugs, and botulinum toxin.
Some women first develop symptoms of myasthenia gravis during early pregnancy or immediately after giving birth, while in other women, the symptoms of myasthenia gravis improve during pregnancy.

Is myasthenia gravis a genetic condition?

Autoimmune myasthenia gravis is not a genetic condition, and it is not inherited from a parent to a child. It is rare for more than one person in a family to have autoimmune MG. There is also a non-autoimmune form called congenital myasthenic syndrome. Congenital myasthenia can affect multiple members of a family.

Approximately 10% of babies born to women with myasthenia gravis develop neonatal myasthenia gravis, which is characterized by weak crying and sucking reflexes. This is a temporary condition, and the symptoms go away on their own in a few weeks. Babies with neonatal myasthenia do not have an increased risk of developing myasthenia gravis as adults.

What are the symptoms of myasthenia gravis?

The main symptom of MG is weakness in certain muscle groups. The symptoms of myasthenia gravis can come on suddenly. Myasthenia symptoms tend to worsen towards the end of the day and improve with rest.

Other symptoms related to muscle weakness include ptosis (drooping eyelids), double vision, difficulty chewing, swallowing, or speaking, weakness of the skeletal muscles in the limbs, problems with holding your head up, lifting your arms above your head, or standing up from a seated position, problems with climbing stairs or walking especially long distances, and shortness of breath when the breathing muscles are affected.

A myasthenia gravis crisis is a complication of MG in which there are worsening symptoms of muscle weakness. People in a myasthenic crisis experience severe breathing problems and respiratory failure. These severe symptoms require emergency treatment, including intubation and mechanical ventilation.

What are the types of MG?

Autoimmune myasthenia gravis is of two types - ocular myasthenia gravis and generalized myasthenia gravis. Ocular myasthenia gravis affects only the eye muscles and causes symptoms like eyelid drooping and double vision. Generalized MG results in muscle weakness in voluntary muscles of the face, head, neck, throat, as well as arm and leg muscles. Almost half of all people with ocular MG develop generalized MG within 2 years of experiencing the first symptom.

How is myasthenia gravis diagnosed?

Healthcare providers can diagnose myasthenia gravis based on your medical history, symptoms, physical exam, laboratory tests, and imaging studies. Some of the tests used for diagnosing myasthenia gravis include:

Neurological exam: Your doctor will check your muscle strength, muscle tone, reflexes, coordination, balance, and senses like touch and sight.
Ice pack test: In people with myasthenia gravis, placing an ice pack on the eyelids or resting with the eyes closed in a dark room for a couple of minutes often improves severe drooping of the eyelids.
Antibody tests: A blood test can be used to detect MG. Approximately 85% of people with myasthenia gravis have high acetylcholine receptor antibody levels. About 6% of MG patients have muscle-specific kinase (MuSK) antibodies. However, antibodies are not detected in under 10% of patients.
Electromyogram (EMG): This test measures electrical activity and can detect problems in communication between nerves and muscles.
Nerve conduction studies: This test measures how well and how fast nerve signals travel.
Repetitive nerve stimulation: This test involves repeatedly stimulating a nerve and measuring muscle fatigability.
Imaging scans: Your doctor may order a CT or MRI scan to check for thymus gland tumors.
Edrophonium test: Edrophonium is a drug which when injected into a vein can temporarily improve eye muscle weakness in people with myasthenia gravis.
Lung function tests: To check respiratory function.

How is myasthenia gravis treated?

There is no cure for myasthenia gravis. However, the following options are available for treating myasthenia gravis:

Medications

Cholinesterase inhibitors can be used to treat myasthenia gravis. These drugs boost communication between nerves and muscles and improve muscle strength. Examples include pyridostigmine and neostigmine.
Immunosuppressants, such as corticosteroids, are used to suppress the body’s immune system response and reduce the production of acetylcholine receptor antibodies.

Intravenous treatments

Intravenous immunoglobulin (IVIG) infusions are given over a period of 2-5 days and contain donor antibodies. IVIG is used to treat generalized MG and myasthenic crisis.
Monoclonal antibodies are biologically engineered proteins given through intravenous infusions. They help to suppress an overactive immune system.
Plasma exchange (plasmapheresis) is done through an IV line to remove abnormal antibodies from the blood.

Physical therapy

Lack of activity in people with neuromuscular disorders can be harmful. Rehabilitation may be useful in a neuromuscular disease such as myasthenia gravis. However, intense physical activity is not recommended for MG patients as it can increase muscle weakness. Therefore, people with myasthenia gravis are advised to find a balance between physical activity and rest to manage their symptoms.

Surgical procedures

Thymectomy surgery involves removing the thymus gland. This surgery may be recommended even if testing does not reveal any thymus gland problems because removal of the thymus gland can sometimes improve myasthenia gravis symptoms.

What is the most common treatment for myasthenia gravis?

The most common treatment for myasthenia gravis is usually an oral medication such as pyridostigmine. This is a cholinesterase inhibitor that helps to boost neuromuscular transmission and reduce muscle weakness. However, the effects only last for a few hours, and you have to take the medicine several times a day.

Can you lead a normal life with MG?

According to the Myasthenia Gravis Foundation, most people with myasthenia gravis can lead near-normal lives. MG is a lifelong condition, but early detection and treatment can help in managing it. The goal of myasthenia gravis treatment is to reduce muscle weakness and prevent breathing and swallowing difficulties.

How do you cope with myasthenia gravis?

The following strategies may help you cope with myasthenia gravis and other neuromuscular diseases:

Safety precautions: Install grab bars and railings for support near stairs and bathtubs. Keep your floors clean and clutter-free to avoid tripping. Keep sidewalks and driveways clear.
Eating routine: Eat at times when your muscle strength is good. Chew your food thoroughly and take breaks between bites to recoup muscle strength. Try eating several small meals throughout the day. Also, try eating soft foods and avoid foods that need a lot of chewing.
Appliances: Electrical appliances and power tools can help you conserve energy. Try using electric can openers, toothbrushes, and other tools for daily tasks.
Eye patch: This can help with double vision, especially while writing or watching TV. Switch between eyes to reduce strain.
Activities: Plan activities such as chores and shopping for a time of day when you have maximum energy.