It has been previously demonstrated that the milder form of oligoarticular JIA (O-JIA), called persistent O-JIA, is associated with an increased frequency and number of Tregs in the inflamed compartment (5, 6) compared with the more severe forms of disease; however, these studies did not stratify according to FOXP3 high or low expression. This evidence concerns the gene FOXP3 and juvenile idiopathic arthritis.