Myasthenia gravis


Myasthenia gravis is a rare long-term condition that causes muscle weakness.

It most commonly affects the muscles that control the eyes and eyelids, facial expressions, chewing, swallowing and speaking. But it can affect most parts of the body.

It can affect people of any age, typically starting in women under 40 and men over 60.

Symptoms of myasthenia gravis

Common symptoms of myasthenia gravis include:

The symptoms tend to get worse when you're tired. Many people find they're worse towards the end of the day, and better the next morning after getting some sleep.

When to see a GP

See a GP if you have long-lasting or worrying symptoms that could be caused by myasthenia gravis.

They'll ask about your symptoms and medical history.

The GP may refer you to a specialist for tests to help diagnose myasthenia gravis or look for other possible causes of your symptoms.

Tests you may have include a blood test, a test to see how well your nerves are working, and some scans, such as a CT scan or MRI scan.

Treatments for myasthenia gravis

Treatments to help keep the symptoms of myasthenia gravis under control include:

  • avoiding anything that triggers the symptoms - some people find that things such as tiredness and stress make their symptoms worse
  • medicine to help improve muscle weakness
  • surgery to remove the thymus gland (a small gland in the chest linked to myasthenia gravis)

If the symptoms suddenly get worse - for example, you develop severe breathing or swallowing difficulties - you may need urgent treatment in hospital.

Outlook for myasthenia gravis

Myasthenia gravis is a long-term condition that typically has phases when it gets worse.

It usually affects most of the body, spreading from the eyes and face to other areas over weeks, months or years. In about 1 in 5 people, only the eye muscles are affected.

It is common for people to have "flare-ups", where symptoms are very troublesome, followed by periods of remission, where symptoms improve.

While remission can sometimes be permanent, this is rare in cases of myasthenia gravis.

If severe, myasthenia gravis can be life-threatening, but it does not have a significant impact on life expectancy for most people.

Cause of myasthenia gravis

Myasthenia gravis is caused by a problem with the signals sent between the nerves and the muscles.

It's an autoimmune condition, which means it's the result of the immune system (the body's natural defence against infection) mistakenly attacking a healthy part of the body.

In myasthenia gravis, the immune system damages the communication system between the nerves and muscles, making the muscles weak and easily tired.

It's not clear why this happens, but it's been linked to issues with the thymus gland (a gland in the chest that's part of the immune system).

Many people with myasthenia gravis have a thymus gland that's larger than normal. Around 1 in 10 people have an abnormal growth of the thymus called a thymoma.

National Congenital Anomaly and Rare Disease Registration Service

If you have myasthenia gravis, your clinical team will pass information about you on to the National Congenital Anomaly and Rare Disease Registration Service (NCARDRS).

The NCARDRS helps scientists look for better ways to prevent and treat myasthenia gravis. You can opt out of the register at any time.


Myasthenia gravis causes muscle weakness that typically has times when it improves and other times when it gets worse.

It often affects the eyes and face first, but usually spreads to other parts of the body over time.

The severity of the weakness varies from person to person. It tends to be worse when you're tired and gets better after resting.

In some people, the symptoms can also have a number of other triggers, such as stress, infections and certain medicines.

Eyes, eyelids and face

Most people with myasthenia gravis have weakness in the muscles of the eyes, eyelids and face.

This can cause:

  • droopy eyelids - affecting 1 or both eyes
  • double vision
  • difficulty making facial expressions

In around 1 in 5 people, only the eye muscles are affected. This is known as "ocular myasthenia".

But for most people, the weakness spread to other parts of the body over a few weeks, months or years.

If you've had symptoms affecting your eyes for 2 years or more, it's unusual for other parts of your body to be affected later on.

Swallowing, speaking and breathing

If the weakness affects the muscles in the mouth, throat and chest, it can cause:

  • difficulty chewing
  • slurred speech
  • a husky, quiet or nasal-sounding voice
  • difficulty swallowing
  • choking and accidentally inhaling bits of food, which can lead to repeated chest infections
  • shortness of breath, particularly when lying down or after exercise

Some people with myasthenia gravis also experience severe breathing difficulties, known as a "mysathenic crisis".

Call 999 for an ambulance immediately if you have worsening severe breathing or swallowing difficulties, as you may need emergency treatment in hospital.

Limbs and other parts of the body

The weakness caused by myasthenia gravis can also spread to other parts of the body, including the neck, arms and legs.

This can cause:

  • difficulty holding the head up
  • difficulty with physical tasks, such as lifting, getting up from sitting to standing, climbing stairs, brushing teeth or washing hair
  • a waddling walk
  • aching muscles after using them

The weakness tends to be worse in the upper body than in the legs and feet.


Myasthenia gravis can be difficult to diagnose and you may need several tests.

First a GP will ask about your medical history and symptoms. Alternatively, an optician may have noticed problems such as double vision or eyelid droop.

If they think you could have a problem with your brain or nerves, they may refer you to a specialist for tests in hospital to help diagnose myasthenia gravis and rule out other conditions with similar symptoms.

Blood test

The main test for myasthenia gravis is a blood test to look for a type of antibody (produced by the immune system) that stops signals being sent between the nerves and muscles.

A high level of these antibodies usually means you have myasthenia gravis.

But not everyone with the condition will have a high level of antibodies, particularly if it's only affecting the eye muscles (ocular myasthenia).

The blood test may be repeated at a later date if the result is normal but your symptoms continue or get worse.

Nerve tests

Your doctor may also suggest an electrical test of your nerves and muscles.

These tests, known as electromyography, involve inserting very small needles into your muscles to measure the electrical activity in them.

The needles are typically inserted around the eyes, in the forehead or possibly in the arms.

The electrical recordings can show whether the signals sent from the nerves to the muscles are being disrupted, which may be a sign of myasthenia gravis.


You may also have a CT scan or MRI scan of your chest to check if your thymus gland is bigger than usual or has grown abnormally (a thymoma).

The thymus gland is a small gland in the chest that forms part of the immune system. Problems with the gland are closely associated with myasthenia gravis.

Sometimes an MRI brain scan may also be carried out to check that your symptoms are not being caused by a problem in your brain.

Edrophonium test

If it's still not clear what's causing your symptoms, the doctor may recommend a test called an edrophonium test.

It involves having an injection of a medicine called edrophonium chloride. If you have a sudden but temporary improvement in muscle strength after the injection, it's likely you have myasthenia gravis.

But this test is rarely done these days because there's a risk it could cause potentially serious side effects, such as a slow heartbeat and breathing problems.

It's only done if absolutely necessary and in a hospital setting where treatment for any side effects is readily available.


Treatment can help keep the symptoms of myasthenia gravis under control so that you're able to live a largely normal life.

But some people need ongoing treatment, and occasionally emergency treatment in hospital may be necessary if the condition suddenly gets worse.

Avoiding triggers

The symptoms of myasthenia gravis can sometimes have a specific trigger. Doing what you can to avoid your triggers may help.

Common triggers include:

  • tiredness and exhaustion - getting plenty of rest and not overexerting yourself may help
  • stress
  • infections - you may be advised to have an annual flu jab and the one-off pneumococcal vaccine, but get advice before having a "live" vaccine, such as the shingles vaccine (live vaccines contain viruses or bacteria that have been weakened)
  • medicines - make sure your doctor is aware of your condition and get advice before taking anything on the list of medicines that can trigger myasthenia gravis symptoms
  • surgery - make sure your surgeon is aware of your condition before having any operation

It's also a good idea to avoid activities that could be dangerous if you have sudden weakness, such as swimming alone. If you drive, you should tell the DVLA you have myasthenia gravis.



The first medicine used for myasthenia gravis is usually a tablet called pyridostigmine, which helps electrical signals travel between the nerves and muscles.

It can reduce muscle weakness, but the effect only lasts a few hours so you'll need to take it several times a day. For some people, this is the only medicine they need to control their symptoms.

Possible side effects include stomach cramps, diarrhoea, muscle twitching and feeling sick. Tell your doctor if you get any of these, as they may be able to prescribe other medicines to help with side effects.


If pyridostigmine does not help or only provides short-term relief, your doctor may suggest taking steroid tablets such as prednisolone.

These work by reducing the activity of your immune system (the body's natural defence against illness and infection), to stop it attacking the communication system between the nerves and muscles.

Prednisolone is usually started in hospital if you have problems with swallowing or breathing, or if your symptoms keep getting worse and you need treatment quickly.

You'll usually be advised to take the tablets every other day. Depending on how severe your symptoms are, you may need to take a high dose at first, which will be gradually lowered as much as possible once your symptoms are under control.

This is because long-term treatment with steroids can cause unpleasant side effects, such as weight gain, mood swings and an increased risk of getting infections.


If steroids are not controlling your symptoms, or you need to take a high dose of steroids, or steroids cause significant side effects, your doctor may suggest taking a different medicine that reduces the activity of your immune system, such as azathioprine or mycophenolate.

These medicines are taken as tablets every day.

It may take at least around 3 months for azathioprine, and around 6 months for mycophenolate, before you start feeling the benefits of the medicine.

Side effects can include an increased risk of getting infections, feeling and being sick, loss of appetite and tiredness. You'll also need to have regular blood tests to check the amount of medicine in your body.

If these medicines keep your symptoms under control for a long time (usually years), it may be possible to eventually stop taking them.


Surgery to remove the thymus gland, known as a thymectomy, may sometimes be recommended if you have myasthenia gravis.

This has been shown to improve myasthenia symptoms in some people with an unusually large thymus (a small gland in the chest), although not in people with a thymus that's grown abnormally (a thymoma).

Symptoms will usually improve in the first few months after surgery, but may keep getting better for 1 to 2 years, and in some cases, for a few more years after that.

Surgery can:

  • reduce the dose of steroids you need to take
  • reduce the chances of needing to take other immunosuppressants
  • reduce the chances of needing to go into hospital because of worsening symptoms

Though it is important to point out that surgery is not always effective and can sometimes make little or no difference to symptoms.

If you have a thymoma, a thymectomy will not usually have much of an effect on your myasthenia symptoms. But surgery to remove your thymus gland will often be recommended because it can cause problems if it's left to keep getting bigger.

Thymectomies are often carried out using keyhole surgery techniques. This is where the thymus is removed using surgical instruments inserted through small cuts (incisions) in the chest.

Emergency treatment in hospital

Some people with myasthenia gravis have periods where their symptoms get suddenly worse – for example, they may experience severe breathing or swallowing problems.

These potentially life-threatening symptoms, known as a mysathenic crisis, require urgent treatment in hospital.

Treatment may include:

  • oxygen through a face mask
  • using a breathing machine (ventilator)
  • intravenous immunoglobulin therapy – a treatment made from donated blood, which improves muscle strength by temporarily changing how your immune system works
  • plasmapheresis – where your blood is circulated through a machine that filters out the harmful antibodies that are attacking the communication system between the nerves and muscles

Help and support

Living with a rare, long-term condition can be very difficult. Some people find it helpful to get in touch with a local or national support group.

The main UK charity for people with myasthenia gravis and their families is myaware.

Myaware provides useful information and advice about living with myasthenia gravis. They also have a Facebook group and local support groups.

The information on this page has been adapted by NHS Wales from original content supplied by NHS UK NHS website
Last Updated: 31/01/2024 14:26:39