Genesis of the Disease
The immune system is a group of cells that normally protects the body from infection. In autoimmune diseases like JM, however, once these cells turn on their infection-fighting process, they cannot turn it off. This process therefore damages the body instead of protecting it.
One way the immune system cells fight infection is through inflammation. But when the cells cannot turn off the inflammation process, tissues are damaged. In JM sufferers, the skin rash and weak muscles are caused by vasculitis, an inflammation in the blood vessels that lie under the skin and in the muscles. Since blood vessels run throughout the human body, JM can also affect other systems such as the digestive tract.
What causes JM?
Many researchers believe that there is a genetic predisposition to autoimmune diseases. As such, they feel that a child afflicted with JM is likely to have a blood relative who suffers from another autoimmune disease such as diabetes or arthritis.
The autoimmune disease initially presents itself when an invasive "trigger" causes the body's immune system to overreact. It is believed that this trigger could be a virus, a vaccine or an environmental hazard.
What are the symptoms of JM?
The primary symptoms of JM are weak or painful muscles, skin rash (with JDM), fatigue and fever. Some children experience joint pain as well.
Here's a news story about a boy's struggle with JM: http://www.nctimes.com/news/local/columnists/morrow/article_7c427faa-93ed-5567-a432-84539f3fc6ca.html