The search for more reliable biomarkers for seronegative arthritis has resulted in several serum proteins that are associated with disease activity in patients with seronegative arthritis: IL-6, IL-17, IL-23, VEGF, and MMP3 in SpA [6, 7, 40–43], and IL-6 and IL-18 in JIA [5, 36, 44], amongst others. This evidence concerns the gene MMP3 and juvenile idiopathic arthritis.