Juvenile rheumatoid arthritis is an autoimmune disorder, which means that the body mistakenly identifies some of its own cells and tissues as foreign. The immune system, which normally helps to fight off harmful, foreign substances such as bacteria or viruses, begins to attack healthy cells and tissues. The result is inflammation--marked by redness, heat, pain, and swelling.
Inflammation is a natural defense of the body to protect against foreign substances or injury, but it can cause problems in certain diseases such as juvenile rheumatoid arthritis.
The Immune System
Doctors do not know why the immune system goes awry in children who develop juvenile rheumatoid arthritis. Scientists suspect that it is a two-step process.