Studies have revealed that myeloid-related protein 8 (MRP-8 (S100A8)) and MRP-14 (S100A9), two calcium-binding S-100 proteins expressed and released by phagocytes, are highly elevated in active disease and may be used for diagnosis and for management of sJIA [5, 6]. This evidence concerns the gene S100A9 and systemic-onset juvenile idiopathic arthritis.