Of note, recent advances in a genetic analysis of juvenile idiopathic arthritis (JIA) revealed that several genetic risks in adult RA patients, such as HLA-DRB1*04 or PTPN22, also confer a risk or a protection on JIA, especially RF-positive polyarthritis, suggesting shared genetic backgrounds between adult seropositive RA and RF-positive JIA [25,26]. This evidence concerns the gene PTPN22 and juvenile idiopathic arthritis.