Myasthenia gravis: Symptoms, diagnosis and treatment
What is myasthenia gravis?
Myasthenia gravis is a rare and chronic condition causing muscles to tire and get weaker easily.
Myasthenia gravis often affects muscles of the eyes and eyelids, the face and those used for chewing and speech.
Muscles used for breathing, and those in the neck, arms and legs can also be affected.
Myasthenia gravis is an autoimmune disorder where the body's defences wrongly turn on nerves and muscles.
Myasthenia gravis symptoms often get worse during exertion and improve once a person rests.
Myasthenia gravis affects around 1 in 10,000 people in the UK, often women under 40 and over 60s men.
The condition cannot be cured, but the symptoms can be managed with treatment.
What causes myasthenia gravis?
Under normal conditions, your nerves direct your muscles to work by sending a message through an area called a receptor. The nerve impulse causes a chemical to be released from the nerve end called acetylcholine. When acetylcholine binds to specific acetylcholine muscle receptors, your muscle knows to contract. In myasthenia gravis, you have fewer acetylcholine receptors than you need.
Myasthenia gravis is considered to be an autoimmune disorder. With an autoimmune disease, some of your body's antibodies (cells in your body that are supposed to be programmed to fight foreign invaders such as bacteria, viruses or fungi) mistake a part of your own body as foreign, resulting in its destruction. In the case of myasthenia gravis, your antibodies block or attack and destroy the acetylcholine receptors needed for muscle contraction.
No one knows exactly what causes your body to begin producing the antibodies that destroy acetylcholine receptors. In some cases, the process seems to be related to the thymus gland which helps produce antibodies.
About one in 10 myasthenia gravis patients are found to have a thymoma, a tumour of the thymus. Although most thymomas are benign, the thymus is often removed (thymectomy) to prevent the potential spread of cancer. In fact, thymectomy seems to improve symptoms of myasthenia gravis in some patients, even if no tumour is present.
Symptoms of myasthenia gravis
The symptoms of myasthenia gravis include:
- Droopy eyelids (ptosis)
- Double vision (diplopia)
- Difficulty swallowing (dysphagia) and an increased risk of gagging and choking
- Change in the quality of one's voice
- Weakness of the muscles in your arms, legs or neck, getting up from sitting, or climbing stairs
- Increasing weakness of a particular muscle group during continuous use of those muscles
- Improved strength of muscles after resting those muscle groups
- Weak cough
- Difficulty breathing, leading to respiratory failure (myasthenic crisis)
Seek medical advice about myasthenia gravis if:
- You notice a new droopy eyelid or double vision.
- You have any difficulty chewing or swallowing.
- You notice intermittent muscle weakness, improved after rest.
- You already have myasthenia gravis and experience any difficulty breathing.