IL1A and systemic-onset juvenile idiopathic arthritis: In particular, systemic juvenile idiopathic arthritis (SJIA), included in the group of juvenile arthritides, has peculiar characteristics deriving from uncontrolled activation of phagocytes with hypersecretion of IL-1 and IL-6, which are opposite in comparison with the other forms of juvenile idiopathic arthritis, the most common chronic rheumatic disease of childhood, i.e. prominent joint involvement, strong association with some HLA class II antigens and eventual positivity of anti-nuclear antibodies, rheumatoid factor or anti-cyclic citrullinated peptide antibodies [65].