Written by Ada’s Medical Knowledge Team
What is myasthenia gravis?
Myasthenia gravis is an autoimmune condition that causes muscles to become weak and quickly tired. In this condition the immune system mistakenly produces proteins that fight infections (antibodies) that attack the the body's healthy tissues. These interfere with the ability of nerves to pass information to muscles. Often the muscles of the eyes and eyelids are affected, causing the common symptoms of eyelid drooping and blurred vision. Muscle weakness typically becomes more noticeable over the course of the day or with exertion and improves on resting. Medication is available that improves the communication between nerves and muscles and thus increases the muscles strength, but there is no sure cure for this condition.
Myasthenia gravis is a rare condition. It occurs when the immune system mistakenly produces proteins that fight infections (antibodies) against parts of the muscles responsible for transmitting impulses from the nerves to make muscles work. This causes the muscles to work slowly and become weak. The reason why this occurs is uncertain, though it is thought than an overactive thymus gland may be partially responsible. Women are slightly more likely than men to develop this condition, and it tends to become more common with age.
The main symptom of myasthenia gravis is a muscle weakness which gets worse over the course of the day. The most commonly affected muscles are the eye, face and throat. People with myasthenia gravis may notice that their eyelids droop, that they develop blurred or double vision or difficulties with chewing, talking or swallowing. Sometimes the muscles of the limbs or the neck can be affected. This may cause problems with walking, posture and balance. People with myasthenia gravis may experience a period during which their symptoms become much worse than normal. These episodes can cause weakness of the breathing muscles and lead to severe breathing difficulty with an inability to cough.
The diagnosis may be suspected based on the symptoms and neurological examination, but a blood test for the antibodies is the only way to confirm the diagnosis. Other tests of nerve and muscle function may help to confirm the diagnosis.
Muscle weakness can be improved by taking medication that improves the communication between nerves and muscles. Medications to dampen the immune system, such as steroids and immuno-suppressant medications, are also commonly used. In cases of a severe deterioration of muscle strength, medications may need to be given through the veins to suppress the immune system. In some cases, removal of the thymus gland can improve the symptoms, but this does not cause immediate improvement.