BAsic information description A chronic inflammatory disease of the joints that affects children. The joints most often involved are the knees, hands, and feet. Symptoms vary from mild to severe. JRA may start at any age in childhood. Major types are: Pauciarticular (limited to a few joints; 40% to 50% of cases). Polyarticular (five or more joints involved; 35% of cases). Systemic-onset (involves at least one joint and involves inflammation of internal organs; 10% to 20% of...