Serum TNF-α, IL-6, and IL-18 levels were nonsignificantly higher in patients with AOSD carrying the AA/CC/TT haplotype (median, 219.0 pg/mL, IQR 219–581.3 pg/mL; 589.2 pg/mL, IQR 589.2–1138 pg/mL; and 778.9 pg/mL, IQR 1778.9–7418 pg/mL, respectively) compared with those carrying the GG/TT/CC or AG/CT/CT haplotype (median, 143.3 pg/mL, IQR 143.3–573.8 pg/mL; 354.4 pg/mL, IQR 354.4–1155.1 pg/mL; and 945.0 pg/mL, IQR 945–6632.9 pg/mL, respectively). This evidence concerns the gene IL6 and adult-onset Still disease.