| || | Diseases and Conditions What Is It? Arthritis involves
inflammation of the joints that causes pain and swelling.
Although many people believe arthritis is a disease of old age,
various forms of arthritis can affect just about anyone at any
age. When arthritis occurs in children younger than age 16, it
is called juvenile arthritis. Approximately 285,000 children in
the United States have some form of the disease. The most common
forms of juvenile arthritis are: - Juvenile rheumatoid
arthritis, also called juvenile idiopathic arthritis -- This is
the most common form of juvenile arthritis. Juvenile rheumatoid
arthritis is thought to be an autoimmune disease, which means
that, for unknown reasons, the body's immune system attacks some
of its own tissue the same way it would react against a foreign
invader such as a virus or bacteria. In juvenile rheumatoid
arthritis, the lining of the joint (called synovial membrane)
becomes inflamed and enlarged, limiting movement and causing
pain and tenderness. Enzymes