Myasthenia gravis is an uncommon condition that causes certain muscles to become weak. With treatment, most people can lead a normal life.
Myasthenia gravis 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 muscles in the arms and legs (see Myasthenia gravis - symptoms). Less often, the muscles involved in breathing may also 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 common in women under the age of 40 and men over the age of 60.
However, in recent years, increasing numbers of patients over the age of 60 are developing the condition.
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 Myasthenia gravis - causes). This blocks the messages that pass from the nerve endings to the 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
Many people with myasthenia gravis become completely free of symptoms with treatment. Sometimes, the symptoms may stop altogether and you can come off treatment.
You may be prescribed tablets that increase chemicals in the body and improve messages from the nerves to the muscles. You may also be given tablets that suppress the immune system (immunosuppressants) and steroid tablets (see Myasthenia gravis - treatment for more information).
Most people with the condition lead a normal, or nearly normal, life.
