Juvenile idiopathic arthritis according to ILAR (International Association of Rheumatology) is a group of chronic arthritis that begins over 6 weeks in children under 16 years old. Clinical manifestations are heterogeneous, including: oligoarticular type; RF (+) polyarticular type; RF (-) polyarticular type; systemic type; psoriatic arthritis type; enthesitis type; unclassified arthritis type. Polyarticular juvenile idiopathic arthritis accounts for 1/3 of this group of diseases.