Serum S100A8 levels were significantly higher in aPL carriers (median 44.3 (IQR 35.6-75.4) ng/mL, p<0.001) and patients with APS (52.8 (37.2-79.2) ng/mL, p<0.001) compared with HCs (25 (21.6-31.1) ng/mL). Here, S100A8 is linked to autoimmune polyendocrinopathy.