Besides joint pain, JRA may cause chronic fever and anemia. In some people, it can also affect the heart, lungs, eyes, and nervous system.
Flare-ups may last for several weeks. Later on, their symptoms may be less severe. Symptoms of JRA may include:
JRA is an autoimmune disorder. This means that the immune system attacks healthy cells and tissues, causing inflammation.
Researchers don't know exactly why it happens. They suspect that it's a two-step process. First, something in a childs genes makes them more likely to develop JRA. Then something else, such as a virus, triggers the disease.