“Juvenile idiopathic arthritis, formerly known as juvenile rheumatoid arthritis, is the most common type of arthritis in children under the age of 16.

Juvenile idiopathic arthritis occurs when the body’s immune system attacks its own cells and tissues. It’s not known why this happens, but both heredity and environment seem to play a role. Some forms of juvenile idiopathic arthritis are more common in girls.”

MAYO CLINIC (https://www.mayoclinic.org/diseases-conditions/juvenile-idiopathic-arthritis/symptoms-causes/syc-20374082)”