The lowdown on myasthenia gravis:
My friend has been diagnosed with myasthenia gravis. Can you tell me something about it?
In normal muscle action, a nerve impulse triggers a nerve ending to release chemicals called neurotransmitters. These transmitters combine with special receptors on the muscle causing the muscle to contract.
In myasthenia gravis the body's immune system destroys many of these receptors so that the muscle becomes less responsive to the nerve impulse. As a result, progressive muscular weakness occurs.
The first muscles to be affected are those of the face and throat, causing weakness of the muscles that control the eyes, eyelids and mouth. Symptoms in the early stages include drooping eyelids, double vision and excessive fatigue after exercise.
As the condition progresses, weakness of the muscles in the arms and legs can develop and difficulties may occur with speaking and swallowing. Approximately 15 per cent of people with the condition experience severe episodes of muscle weakness, called myasthenia crisis.
A small proportion of people who experience a myasthenia crisis suffer acute weakness of the muscles needed for breathing, a condition that can be life threatening.
Do we know why the illness happens?
We are not entirely sure why this condition occurs. However, one theory is that a malfunction of the thymus gland, located in the upper part of the chest, may be related to the production of the abnormal antibodies.
Who is more likely to get it?
The condition is more common in women and usually develops between the ages of 20 and 40. The disorder occurs less frequently in men, but can do so at any age.
Can it be treated?
A range of treatments are available to help control the condition. These include removal of the thymus gland, removal of abnormal antibodies from the body in a process called plasmapheresis and treatment with drugs that aim to improve the muscles' response to nerve function. These may be administered alone or with other drugs that depress the immune system.
Medications may cause unwanted side effects such as vomiting, nausea, diarrhoea and muscle cramps in the arms legs and abdomen.