Cytokine profile in adult-onset Still's disease: Comparison with systemic juvenile idiopathic arthritis.

To compare pro-inflammatory cytokine profiles and kinetics in patients with adult-onset Still's disease (AOSD) to those in patients with systemic juvenile idiopathic arthritis (s-JIA), we analyzed serum cytokine concentrations in 33 patients with AOSD and 77 patients with s-JIA and compared them with clinical features. Patients with AOSD and s-JIA shared a common cytokine profile pattern of a significant increase in IL-18. Patients with AOSD were classified into two subgroups based on serum IL-6 and IL-18 levels. The number of patients with arthritis was significantly higher in the IL-6-dominant subgroup. The cytokine patterns associated with s-JIA and AOSD share common features, such as a significant and predominant increase in IL-18. Distinct IL-6- and IL-18-based cytokine profiles might be responsible for distinct clinical manifestations. The presence of two distinct subgroups in patients with both diseases further supports the view that s-JIA and AOSD share a disease category.