S100A9 and systemic-onset juvenile idiopathic arthritis: Other cytokines that may play a role in sJIA are interleukin-18 (IL-18) [28], myeloid-related protein (MRP)-8 and MRP-14 [29, 30], macrophage migratory inhibitory factor (MIF) [31], and interleukin 4-1098 T/G polymorphism [32].