What Is Myasthenia Gravis?

Are you experiencing drooping of your eyelids or double vision? These symptoms can be seen in many different health conditions, but they can also be a sign of myasthenia gravis. This is a rare autoimmune disease that causes your muscles to become weaker, commonly in areas such as your eyes. It can also affect your chewing, swallowing, and breathing ability. 

In extreme cases, a myasthenic crisis can occur  when the muscles that help you breathe become too weak and a ventilator is required to help with breathing. Myasthenia gravis is a long-term health condition that can be very difficult to live with, but there are treatments to help with the symptoms and improve a person’s day-to-day life.

This article will help you understand what myasthenia Gravis is by focusing on what the condition is, what causes it, the signs and symptoms of myasthenia gravis, and the treatment choices available.

Overview

Myasthenia gravis is an autoimmune disorder that results in muscle weakness and fatigue.¹ It is caused by the immune system attacking the body’s cells and this results in poor nerve-muscle communication. This means that it becomes much harder to move or control your muscles voluntarily. Myasthenia gravis characteristically affects the eye muscles, but it also affects other muscles.¹

There are two main types of myasthenia gravis – ocular and generalised. In ocular myasthenia gravis, the eyelids and eye muscles are affected whereas in generalised myasthenia gravis other parts of the body such as the arms, legs, or face are affected as well. If myasthenia gravis is detected in childhood or adolescence then it is termed juvenile myasthenia gravis.²

Myasthenia gravis is a rare autoimmune disease and it is seen in around 15 people per 100,000 people in the UK.³ According to the NHS, it is more commonly seen in women below 40 years of age and men above 60 years of age, but it can present at any stage of life. Rarely infants may suffer from a condition known as neonatal myasthenia gravis which is a temporary form of the condition and usually lasts a few months after birth.⁴ This is seen in infants whose mother suffers from myasthenia gravis.⁴ Congenital myasthenic syndrome is seen in infants or children and is an inherited disorder. It is caused by a faulty gene that produces an abnormal protein resulting in poor nerve-muscle communication.

Causes of myasthenia gravis

Myasthenia gravis is an autoimmune condition which means that the immune system attacks the body’s cells.¹ In the case of myasthenia gravis, the nerve signals are not transmitted to the muscles correctly so they don’t contract properly. Usually, nerves send signals or impulses through a neuromuscular junction to the muscles.⁵ The electrical signals or impulses are sent down the motor nerve and when it reaches the end of the nerve, a neurotransmitter called acetylcholine is released.⁵ Neurotransmitters, such as acetylcholine, help the nerves and muscles communicate. When acetylcholine is released into the neuromuscular junction, it binds to acetylcholine receptors on the muscle and triggers muscle contraction to occur.⁵ But, in myasthenia gravis, antibodies are produced and they attack these acetylcholine receptors found on the muscles.⁵ This means that the nerve-muscle communication doesn’t work as effectively and therefore the muscles don’t contract. It is not known why this autoimmune response occurs.

Likewise, myasthenia gravis can be caused by an abnormal thymus gland, which is found in the upper chest.⁶ The thymus gland is important in regulating and keeping the immune system functioning correctly. Many people with myasthenia gravis have a large thymus gland and sometimes people can develop a thymoma. This is a tumour in the thymus gland that is usually noncancerous, but in certain cases, it may become cancerous. Abnormalities of the thymus gland may cause myasthenia gravis because it doesn’t eliminate the antibodies that attack the acetylcholine receptors on the muscle.⁶ This in turn affects nerve-muscle communication which causes muscle weakness and fatigue. 

Signs and symptoms of myasthenia gravis

Myasthenia gravis can affect people differently depending on whether they experience ocular or generalized myasthenia gravis. Symptoms may start suddenly and progressively get worse. Usually, myasthenia gravis affects the eyelids and eye muscles first and over time can affect the legs, arms, face, neck, and other muscles. Symptoms can become more noticeable as the day goes on or when you are tired and improve after rest or sleep.⁷ Symptoms can also become worse due to triggers such as stress, heat, and infections.

The common symptoms associated with myasthenia gravis are:⁷

• Drooping of the eyelid(s)
• Double vision or blurred vision
• Difficulty chewing or swallowing
• Difficulty speaking or impaired speech
• Shortness of breath
• Changes in facial expressions or being expressionless
• Weakness in the eye, arm, leg, face, or neck muscles
• Difficulty holding head up
• Difficulty performing physical tasks such as climbing stairs
• Difficulty walking

People who have myasthenia gravis can experience different symptoms of varying severity. If you are experiencing any of these symptoms or are worried about any of the symptoms mentioned then it is important to speak to a healthcare professional.

In severe circumstances, people may find that they struggle to breathe or cannot breathe because the muscles in the respiratory system are so weak. This is known as a myasthenic crisis and it is a medical emergency that requires treatment immediately.⁷ If someone is having a myasthenic crisis, they will be put on a ventilator to help them breathe.⁷  

Myasthenia gravis can be difficult to diagnose because the symptoms are seen in other health conditions. A doctor can help to diagnose myasthenia gravis and they will discuss your symptoms with you as well as check your medical records. Different examinations and tests will also be carried out.⁷ Initially a doctor may carry out a neurological examination where they check your reflexes, balance, coordination, and muscle strength. They may also carry out a blood test to check if you have abnormal antibodies present that affect nerve-muscle communication and cause muscle weakness. If you have problems with your eyelids drooping, an ice pack test can be used to see if any improvement is seen after placing the ice pack on your eyelids.⁷ A CT scan or MRI scan is used to check for abnormalities or tumours located in the thymus gland. Other more complex diagnostic tests include an edrophonium chloride test and nerve tests (known as repetitive nerve stimulation and single fibre electromyography).⁷

Management and treatment for myasthenia gravis

If you are diagnosed with myasthenia gravis, there are different treatment options available to help control the symptoms. Treatment will depend on your symptom severity and disease progression. The medication will need to be taken long-term and you may require a combination of different medications.

The medication used to help alleviate the symptoms associated with myasthenia gravis are:

Cholinesterase inhibitors - These are used first-line for treatment with pyridostigmine commonly used.⁸ They help to improve nerve-muscle communication. Pyridostigmine does this by stopping the neurotransmitter acetylcholine from being broken down.⁸ This means that muscle contraction is improved as the signal sent from the nerves is received by the muscles. The effects of the medication are short lasting so it needs to be taken several times a day to control symptoms.⁸ Side effects that are associated with this medication include nausea, diarrhoea, increased sweating, and abdominal cramps.⁸

Corticosteroids – This class of medication is used when symptoms cannot be adequately controlled by using cholinesterase inhibitors alone. They are steroids with prednisolone being commonly used.⁸ Prednisolone works by lowering the activity of the immune system so fewer antibodies against acetylcholine receptors are produced. This means that signals sent from the nerves can be passed down to the muscles so they contract. If someone is started on corticosteroids for myasthenia gravis then it will be a long-term course.⁸ Taking corticosteroids long-term can cause many unpleasant side effects which the doctor will discuss with you.⁸ This may include weight gain, weakening of the bones, mood swings, and an increased risk of infection.⁸

Immunosuppressants – These are used when corticosteroids aren’t working effectively, if you are taking a high dose, or if you experience many side effects. Commonly azathioprine or mycophenolate are used.⁸ They help to reduce the activity of your immune system which helps with nerve-muscle communication. This medication takes a while to start being effective – around 8-12 months.⁸ This means that you will have to take it alongside one of the treatments mentioned above. The side effects of immunosuppressants are nausea, vomiting, fatigue, and an increased risk of infection.⁸

Apart from medication, in some cases, surgery is recommended for myasthenia gravis. This is offered to people who have a large thymus gland and can help with the symptoms.⁸ If someone is experiencing a myasthenic crisis where they can’t breathe properly then this is a medical emergency and the person needs to be treated in a hospital. They will usually be put on a ventilator to help them breathe and receive medication.⁸ 

FAQs

How is myasthenia gravis diagnosed? 

Myasthenia gravis can be hard to diagnose so it may be necessary to do different tests and examinations. These may include a neurological exam, ice pack test, blood test, nerve test, edrophonium chloride test, and various scans.

How can I prevent myasthenia gravis? 

There aren’t any known ways by which you can prevent myasthenia gravis. 

What are the types of myasthenia gravis? 

The two main types of myasthenia gravis are ocular myasthenia gravis and generalized myasthenia gravis. Rarer types include neonatal and juvenile myasthenia gravis. The congenital myasthenic syndrome is a related condition.

Who are at risk of myasthenia gravis? 

Age may be a risk factor - women could be more at risk of developing myasthenia gravis between 20 to 30 years of age, whereas men have an increased chance of developing the condition between 60 to 70 years of age. 

How common is myasthenia gravis? 

Myasthenia gravis is a rare disease with around 15 people per 100,000 people in the UK having the condition.³ 

When should I see a doctor? 

If you experience any signs or symptoms of myasthenia gravis or have any concerns relating to the condition then you should speak to your doctor. If someone has a myasthenic crisis, this is a medical emergency.

Summary

Myasthenia gravis is a rare life-long autoimmune disease that is characterized by muscle weakness and fatigue. This weakness results from the nerve-muscle connection not working properly. Usually, the eyelids and eye muscles are affected first, and later other body muscles become involved. Myasthenia gravis occurs due to an autoimmune response which means the body’s immune system attacks its cells, in this case, antibodies against the acetylcholine receptors are produced. A large thymus gland may also play a part. Symptoms that are experienced include eyelid drooping, difficulty swallowing, chewing, or double vision. Once a diagnosis is made there are different medication options to help people with their symptoms so they can lead a normal day-to-day life. Sometimes the muscles can become too weak and a myasthenia crisis occurs where the person cannot breathe properly so they require urgent medical attention. It is important to speak to your doctor if you have any symptoms or concerns relating to myasthenia gravis.