Myasthenia gravis

Myasthenia gravis is a condition that causes some muscles around your body to become weak. It literally means 'grave muscle weakness'.

The condition can affect any muscles that you can control voluntarily. Muscles that you cannot control voluntarily, such as the heart muscles, are not affected.

Myasthenia gravis most commonly affects the muscles that control eye and eyelid movement, facial expression, chewing, swallowing and talking, and the arms and legs (see Symptoms). Less often, the muscles involved in breathing may be affected.

The muscle weakness is usually made worse by physical activity and improved by rest.

How common is it?

Myasthenia gravis affects about one person in every 10,000 in the UK. It can develop at any age, but is most common in women under the age of 40 and men over the age of 60.

What is the cause?

Myasthenia gravis is an autoimmune disease, which means that your immune system attacks your own body tissues. In the case of myasthenia gravis, your immune system produces antibodies that block or damage your muscle receptor cells (see Causes). This affects normal communication between your nerves and muscles, so your muscles do not contract well and become weak.

The reason why some people's immune systems make antibodies against muscle receptor cells is not fully understood.

Outlook

There is no cure for myasthenia gravis, but many people with the condition become completely free of symptoms with treatment, which includes immunosupressants and steroid tablets (see Treatment). Most are able to lead a normal, or nearly normal, life.

Glossary

Heart

The heart is a muscular organ. Its function is to pump blood around the body