Definition of Juvenile rheumatoid arthritis:

Juvenile rheumatoid arthritis (JRA) is a general term for the most common types of arthritis in children. It is a long-term (chronic) disease resulting in joint pain and inflammation, which may lead to joint damage.

Causes, incidence, and risk factors:

JRA occurs in 50-100 per 100,000 children in the United States. It usually occurs before age 16.

JRA is divided into several categories:

• Systemic JRA occurs in about 10% of cases. It involves joint pain, swelling, fevers, and rash. It is similar to adult Still's disease. The cause of this form of JRA is unknown.
• Polyarticular JRA occurs in about 40% of cases and involves multiple painful, swollen joints. The cause of this form of JRA is also unknown. Some children may have a positive rheumatoid factor and the condition may turn into rheumatoid arthritis.
• Pauciarticular JRA occurs in about 50% of cases and involves only a few joints. Some of these children, in particular boys, will be HLA-B27 positive. HLA-B27 is a substance called a gene marker that is associated with several autoimmune disorders.