Myasthenia gravis: symptoms, causes, tests and treatment

The NHS says 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, then usually spreads to other parts of the body over time. The severity varies from person to person.

Most people have weakness in the muscles of the eyes, eyelids and face. If symptoms have been confined to the eyes for 2 years or more, the NHS says it is unusual for other parts of the body to be affected later on. For some people only the eye muscles are involved, which is known as ocular myasthenia.

Symptoms tend to be worse when you are tired and better after resting. The NHS says other triggers can include stress, infections and certain medicines.

Muscles move because nerves send them signals. In myasthenia gravis the NHS explains there is a problem with the signals sent between the nerves and the muscles. It is an autoimmune condition, meaning the immune system mistakenly attacks a healthy part of the body. Here it damages the communication system between nerves and muscles, making the muscles weak and easily tired.

myaware, the main UK charity for the condition, describes the myasthenias as a group of neuromuscular conditions that are rare but manageable. It points out that the weakness is in the voluntary muscles, the ones you control, such as the arm and leg muscles, and that people typically notice the harder they try, the weaker they get.

NHS inform describes myasthenia gravis as a long-term (chronic) condition. It is not the same as the other myasthenias, which are compared in the table below.

The NHS says treatment can help keep symptoms under control so that you are able to live a largely normal life. Some people need ongoing treatment, and occasionally emergency treatment in hospital is needed if the condition suddenly gets worse. Treatment is planned by a specialist team, not by a single fixed recipe.

Medicines follow a step pattern in the NHS description. Pyridostigmine is usually first. It helps electrical signals travel between nerves and muscles and can reduce muscle weakness, but the effect lasts only a few hours so it is taken several times a day. For some people it is the only medicine needed. Possible side effects include stomach cramps, diarrhoea, muscle twitching and feeling sick.

If pyridostigmine does not help or gives only short-term relief, a doctor may suggest steroid tablets such as prednisolone. These reduce immune system activity. The NHS says they are usually taken every other day, often starting at a higher dose that is gradually lowered, because long-term steroids can cause weight gain, mood swings and a higher risk of infection.

If steroids are not controlling symptoms, a high dose is needed or side effects are significant, other immunosuppressants such as azathioprine or mycophenolate may be suggested. The NHS says it may take at least around 3 months for azathioprine and around 6 months for mycophenolate before you feel the benefit, and that regular blood tests are needed. If these medicines keep symptoms under control for years, it may be possible to stop them.

Surgery to remove the thymus gland (thymectomy) is sometimes recommended. The NHS says it has been shown to improve symptoms in some people with an unusually large thymus, but not usually in people who have a thymoma. Symptoms usually improve in the first few months and may keep improving for 1 to 2 years. Surgery is not always effective, and it is often done by keyhole techniques.

• Avoid known triggers: tiredness, stress, infections, some medicines and surgery.

• The NHS says you may be advised to have an annual flu jab and the one-off pneumococcal vaccine, but to get advice before a live vaccine such as the shingles vaccine.

• Tell any doctor or surgeon you have myasthenia gravis before new medicines or operations.

• If you drive, tell the DVLA you have myasthenia gravis.

The NHS says it is not clear why the immune system attacks the nerve-to-muscle signals, but the condition has been linked to problems with the thymus gland, a small gland in the chest that is part of the immune system. Many people with myasthenia gravis have a thymus gland that is larger than normal, and around 1 in 10 people have an abnormal growth of the thymus called a thymoma.

The NHS and NHS inform both describe triggers for symptoms (tiredness, stress, infections, some medicines, surgery) rather than a single cause. These can make symptoms flare in someone who already has the condition.

The NHS says myasthenia gravis can be difficult to diagnose and you may need several tests. A GP asks about your symptoms and medical history. An optician may notice problems such as double vision or eyelid droop. You may then be referred to a specialist for tests to confirm it and rule out conditions with similar symptoms.

• Blood test: the main test looks for a type of antibody that stops signals passing between the nerves and muscles. It may be repeated later if the result is normal but symptoms continue or get worse.

• Nerve tests: electromyography (EMG) uses very small needles in the muscles, typically around the eyes, forehead or arms, to measure electrical activity and show whether signals from nerve to muscle are being disrupted.

• Scans: a CT or MRI scan of the chest checks whether the thymus is bigger than usual or has a thymoma. Sometimes an MRI brain scan checks that symptoms are not caused by a brain problem.

• Edrophonium test: an injection that briefly improves strength if the condition is present. The NHS says it is rarely done because of a risk of serious side effects such as a slow heartbeat and breathing problems, and is only done in hospital if absolutely necessary.

Some people have severe breathing difficulties, known as a myasthenic crisis. The NHS says to call 999 for an ambulance immediately if you have worsening severe breathing or swallowing difficulties, because you may need emergency treatment in hospital. NHS inform adds that you should phone 999 or go to A&E if you have severe breathing or swallowing problems, and that it is possible to have a crisis before you know you have the condition.

Hospital treatment for a crisis can include oxygen through a face mask, a breathing machine (ventilator), intravenous immunoglobulin (IVIG) or plasma exchange. NHS inform says plasma exchange and IVIG can offer quick improvement within a few days, and although the benefit lasts only weeks, this can give time for longer-term treatments to take effect.

Outside a crisis, see a GP if you have long-lasting or worrying symptoms that could be caused by myasthenia gravis, such as droopy eyelids, double vision, or weakness that is worse when tired. NHS inform also advises avoiding activities that could become dangerous if you have sudden weakness, such as swimming alone.

The NHS describes myasthenia gravis as a long-term condition that typically has phases when it improves and phases when it gets worse. Flare-ups are common, followed by periods of remission. While remission can sometimes be permanent, the NHS says this is rare. If severe it can be life-threatening, but it does not have a significant impact on life expectancy for most people.

NHS inform says that during pregnancy or after having a baby, myasthenia gravis may worsen. If you are planning a pregnancy or become pregnant, speak to your healthcare team and do not stop taking your medicines without speaking to a healthcare professional first.

The NHS says your clinical team will pass information about you to the National Congenital Anomaly and Rare Disease Registration Service, and you can opt out of the register at any time.

In the NHS pathway a GP is usually the first step. The NHS says the GP may refer you to a specialist for blood tests, nerve tests and scans. Ongoing care, including medicines and any thymus surgery, is typically coordinated by a neurology team.

Some people choose to see a neurologist privately for an assessment or a second opinion. In general terms the same types of tests and treatments apply, and the main practical questions are which tests are included, who will manage long-term monitoring such as blood tests for immunosuppressants, and how the private team will share information with your GP.

myaware provides information and support for people with myasthenia and their families, and the NHS points to it as the main UK charity for the condition.