Juvenile idiopathic arthritis (JIA) is a heterogeneous group of chronic inflammatory rheumatic diseases beginning before the age of 16. The most common pediatric rheumatologic disease. JIA is the most common pediatric rheumatologic disease. Apart from clinical features and the biological inflammatory syndrome, no predictive parameter for the severity of JIA, especially polyarticular JIA, has been identified. The team has been interested in the prognosis of RA for many years. Thus, the investigators have conducted various studies in search of biological parameters associated with the joint prognosis of RA patients, which allowed the investigator to discover the interest of angiogenic and inflammatory biomarkers such as semaphorins and CCN1 protein. This has been demonstrated in vitro but also in vivo from sera of RA patients. These markers are associated with activity and structural damage in RA.~The project aims to study the interest of these same angiogenic biomarkers in the serum of JIA patients in order to establish whether, as in RA, they are also associated with disease severity.
The aim of the study is to determine whether serum inflammatory angiogenic markers (eg, semaphorins, CCN1) predict severity of juvenile idiopathic arthritis defined by structural progression and/or therapeutic escalation.