Compared to control neutrophils, cells from children with active SJIA displayed a proinflammatory gene expression signature, including upregulation in PRR, inflammasome components, and the IL-18 receptor component IL18RAP. Although this sequencing was performed on highly purified but unsorted neutrophils, these changes are likely not solely due to the presence of CD16+CD62Ldim neutrophils in active disease. Here, IL18RAP is linked to systemic-onset juvenile idiopathic arthritis.