Recent research has demonstrated that IL-17A and/or IL-17F play a role in the development of inflammation in a variety of disorders, particularly in autoimmune conditions like rheumatoid arthritis (RA), psoriasis, juvenile idiopathic arthritis (JIA), Crohn’s disease and various others.9–12 It has been suggested that the previously mentioned immune mediators with polymorphic gene sequences represent potential markers of an individual’s susceptibility to JIA.13–15. Here, IL17F is linked to juvenile idiopathic arthritis.