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:
In around one in five people, the condition only affects the eye muscles. This is known as "ocular myasthenia".
But for most people, the weakness spreads to other parts of the body over a few weeks, months or years.
If you've only had symptoms affecting your eyes for two 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:
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.