There have been several previous biomarker discovery efforts in SJIA. Initial studies, including ours [2] , attempted to identify early clinical variables that predict long-term outcomes, such as joint damage or functional disability at ≥2 years after disease onset [3] [4] [5] [6] . Studies of serum found elevated cytokines, chemokines, and acute-phase reactants in active SJIA [7] [8] [9] [10] . More recently, transcriptional profiling of peripheral blood mononuclear cells from SJIA subjects with active disease revealed a signature of active SJIA that normalized in association with clinical response to treatment [11, 12] . A single SELDI-based analysis of plasma identified serum amyloid A as a plasma biomarker of disease activity [13] . However, all these efforts fall short of robust diagnostic and prognostic biomarkers with practical clinical utility.