Elevated levels of circulating CLEC5A-expressing monocytes and granulocytes, CLEC5A overexpression on PBMCs in our AOSD patients, and the positive correlation between CLEC5A levels and disease activity or inflammatory parameters of AOSD suggest that CLEC5A may be involved in AOSD pathogenesis and potentially serve as an activity indicator. This evidence concerns the gene CLEC5A and adult-onset Still disease.