Myasthenia Gravis – The Body Attacking Its Own Muscles

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What is it?

Myasthenia gravis is a disease in which there is muscle weakness and fatigue.

Who gets it?

It usually happens around the ages 20-30 and after age 50 (but can occur anytime in life). When it appears in ages 20-30 it’s more common in women, while after age 50 it’s more common in men.

What causes it?

In order to understand this, we need to understand what usually causes a muscle to contract. 

Our muscles are controlled by signals they get from our spinal cord or brain. When you need to move a muscle, that signal travels from the spinal cord through a nerve, and then reaches the area where the nerve is attached to the muscle. This area is called a neuromuscular junction.

neuromuscular-junction

 

In order for the muscle to understand that it should contract, the nerve releases a molecule called acetylcholine. When acetylcholine reaches the muscle, it enters it by plugging into a special receptor, which lets it enter the muscle. That will cause the muscle to contract.

In myasthenia gravis, antibodies (the molecules in our body usually responsible for fighting infections) attack the receptor. No one really knows why, but this auto-attack can also be seen in other diseases (see lupus, vitiligo, graves disease). As a result of this attack, the receptors get blocked by antibodies, and eventually get destroyed. This leads to muscle weakness, since the nerve can’t transmit its signal to the muscle properly.

How does it feel?

People with myasthenia get tired quickly after using their muscles. This will improve after they rest. The muscles that are most involved are those of the eyes and the face.

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A man with myasthenia gravis. You can see that his left eyelid is dropping, due to muscle weakness. (Photo by Cumulus)

In some people, the disease will only involve the eyes or face muscles, while in others other muscles may also be involved, including the legs, arms and even the muscles responsible for breathing.

How is it discovered?

A drug called edrophonium is used. This drug increases the concentration of acetylcholine in the neuromuscular junction, which causes it to overcome the weakness causes by the disease. It works for only 5 minutes, in which you can see the symptoms go away.

There is also a need to perform other tests, such as testing the blood for antibodies against the acetylcholine receptor or checking the function of the nerves.

How is it treated?

There are several ways to treat myasthenia gravis:

  1. Specific drugs: These cause the level of acetylcholine in the junction to increase, much like the edrophonium drug used to discover the disease. But these work for longer than 5 minutes. These drugs do not cure the disease – only overcome the symptoms.
  2. Drugs that weaken the immune system: We said above that the body’s immune system attacks the body itself. Using drugs like steroids, or other drugs that weaken the immune system, slows down the disease. This also doesn’t cure it.
  3. Surgery: Sometimes, removal of the thymus gland (which our body doesn’t use anymore after adolescence anyway) may cure the disease.

What happens after treatment?

That depends on how severe the disease is in a specific person – in some people it affects more muscles than in others.  In most people, drug therapy is needed for a lifetime.

You can see in this video that even with a full blown disease, a normal life and beyond can be achieved:


The bottom line: How do I avoid it?

There are no known ways to prevent myasthenia gravis.

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Posted in Whole Body
 

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