### Juvenile Idiopathic Arthritis (JIA) Overview Juvenile idiopathic arthritis (JIA), previously known as juvenile rheumatoid arthritis (JRA), is a type of arthritis that causes joint inflammation and stiffness in children aged 16 or younger. It affects around 50,000 children in the United States. The inflammation can cause redness, swelling, warmth, and soreness in the joints, although many children may not complain of joint pain. Any joint can be affected, and the inflammation may limit the mobility of the affected joints. ### Causes and Symptoms JIA is an autoimmune disorder, meaning the body's immune system mistakenly attacks its own cells and tissues. Researchers believe that a combination of genetic factors and environmental triggers, such as a virus, may cause JIA. Symptoms can include fever, anemia, and can also affect the heart, lungs, eyes, and nervous system. Arthritic episodes can last for several weeks and may recur, but symptoms tend to be less severe during later attacks. ### Types of JIA Doctors classify JIA into three main types based on the number of joints involved, symptoms, and the presence of certain antibodies in the blood. These classifications help in understanding how the disease will progress. ### Treatment Treatment for JIA is similar to that for adults, with a strong emphasis on physical therapy and exercise to keep growing bodies active. Many strong medicines used for adults are not usually needed for children with JIA. Permanent damage from JIA is now rare, and most affected children recover fully without lasting disabilities. ### Differences Between Juvenile and Adult Arthritis One key difference between juvenile and adult arthritis is that some children with JIA outgrow the illness, while adults usually have lifelong symptoms. Studies estimate that by adulthood, JIA symptoms disappear in more than half of affected children. Additionally, JIA may affect bone development and growth, unlike adult rheumatoid arthritis. Another difference is the presence of rheumatoid factor in the blood; fewer than half of children with JIA are rheumatoid factor positive, compared to 70-80% of adults with rheumatoid arthritis.