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. According to the Arthritis Foundation, about 300,000 children in the United States have some form of the disease.
The most common forms of juvenile arthritis are:
- Juvenile idiopathic arthritis (formerly called juvenile rheumatoid arthritis) – This is the most common form of juvenile arthritis. Juvenile idiopathic 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 idiopathic arthritis, the lining of the joint (called synovial membrane) becomes inflamed and enlarged, limiting movement and causing pain and tenderness. Enzymes released by the inflamed membranes cause further damage by eroding the bone and cartilage. This type of joint and bone damage can cause problems in a growing child. If the growth areas of the bones are affected, the bones may grow at different rates so that one bone may develop abnormally in shape or size. The result could be, for example, that one leg might be permanently shorter than the other.
There are several subcategories of juvenile idiopathic arthritis, including: