Myasthenia gravis is a rare long-term condition that causes certain muscles to become weak.

It mainly affects muscles that are controlled voluntarily often those controlling eye and eyelid movement, facial expression, chewing, swallowing and speaking.


Sometimes, the muscles that control breathing, neck and limb movements are alsoaffected.

The muscle weakness associated with myasthenia gravis is usually worse during, or just after, physical activity and improves with rest. The symptoms are often described as being at their worst when a person is tired, for example, at the end of the day.


In myasthenia gravis, the immune system produces antibodies (proteins) that block or damage muscle receptor cells.

This prevents messages being passed from the nerve endings to the muscles, which results in the muscles not contracting (tightening) and becoming weak.

It's not fully understood why some people's immune systems produce specific antibodies thatblock the nerve's signal to themuscle.

They may suspect myasthenia gravisif youreye movements are impairedor if you have muscle weakness but you're still able to feel things. Around half of people with myasthenia gravis initially develop symptoms of double vision or eyelid droop, with more than 90% of people developing these symptoms at some point during the illness.

You may be referred to a neurologist (specialist innervous system disorders), whowill carry out sometests to help confirm the diagnosis.

The thymus gland is found underneath the breastbone and is part of the immune system. It's often abnormal in people withmyasthenia gravis.

Removing a thymus gland tumour (thymoma) usually has little or no effect on the underlying myasthenia gravis.

Who is affected by myasthenia gravis?

Myasthenia gravis is a rare condition, affecting about 15 in every 100,000 people in the UK.

It can develop at any age, but most commonly affects women under 40 years of age and men over 60. Cases of myasthenia gravis are increasing, particularly in people over 50, but the reasons for this increase aren't fully understood.

Information about you

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

This helps scientists look for better ways to prevent and treat this condition. You can opt out of the register at any time.

Find out more about the register.

Content supplied by the NHS Website

Medically Reviewed by a doctor on 24 May 2016