S100A12 is a novel molecular marker differentiating systemic‐onset juvenile idiopathic arthritis from other causes of fever of unknown origin

S100A12, a marker of granulocyte activation, is highly overexpressed in patients with systemic-onset JIA or FMF, which may point to as-yet unknown common inflammatory mechanisms in these diseases. The measurement of S100A12 serum levels may provide a valuable diagnostic tool in the evaluation of FUO.