What causes JIA?
We don't completely understand what causes JIA. In fact, that's what ‘idiopathic’ means.
What we do know is that JIA is an autoimmune disease. Your immune system is your body’s way of defending itself against injury, illness or bacteria.
Your body can defend itself by causing inflammation or swelling. But when you have JIA, your body creates inflammation in a joint or joints when it doesn’t need to. This inflammation then causes stiffness and pain.
Is JIA genetic?
It's very rare to have two people in the same family with JIA, but we do know that genetic factors are involved. This is to do with the genes that are passed down from your parents.
JIA is thought to be due to a combination of genetic factors and trigger factors from the environment, for example the infections that your immune system has been in touch with.
There’s no evidence that a specific infection causes JIA, but an infection may trigger your immune system's response that then carries on and affects your joints.