A recent study investigated CD4+CD25+ Treg cells in children with persistent oligoarthritis (1–4 joints affected at diagnosis and throughout the disease course) and extended oligoarthritis (a more destructive disease course in which the number of affected joints increases beyond 4 within 6 months of disease onset), hypothesizing that Treg cells may play a role in the reversal of the autoimmune disease process in patients with persistent oligoarticular JIA (23). This evidence concerns the gene CD4 and oligoarticular juvenile idiopathic arthritis.