Purpose of review: This review summarizes biomarkers in systemic juvenile idiopathic arthritis (sJIA). Broadly, the markers are classified under protein, cellular, gene expression and genetic markers. We also compare the biomarkers in sJIA to biomarkers in cryopyrin-associated periodic syndrome (CAPS).
Recent findings: Recent publications showing the similarity of clinical response of sJIA and CAPS to anti-interleukin 1 therapies prompted a comparison at the biomarker level.
Summary: sJIA traditionally is classified under the umbrella of juvenile idiopathic arthritis. At the clinical phenotypic level, sJIA has several features that are more similar to those seen in CAPS. In this review, we summarize biomarkers in sJIA and CAPS and draw upon the various similarities and differences between the two families of diseases. The main differences between sJIA and CAPS biomarkers are genetic markers, with CAPS being a family of monogenic diseases with mutations in NLRP3. There have been a small number of publications describing cellular biomarkers in sJIA with no such studies described for CAPS. Many of the protein marker's characteristics of sJIA are also seen to characterize CAPS. The gene expression data in both sJIA and CAPS show a strong upregulation of innate immunity pathways. In addition, we describe a strong similarity between sJIA and CAPS at the gene expression level in which several genes that form a part of the erythropoiesis signature are upregulated in both sJIA and CAPS.