The candidate genes were selected from promising biomarkers of PJI reported previously for (i) synovial fluid, namely, DEFA1 (coding for alpha-defensin), LTF (lactotransferrin), CRP (C-reactive protein), BPI (bactericidal/permeability-increasing protein), IL1B (interleukin 1 beta), DEFB4A (beta-defensin 4), and IFNG (gamma interferon) (4, 12), and (ii) periprosthetic tissue and serum, namely, TLR1 (Toll-like receptor 1), TLR2, TLR4, TLR6, and TLR10 (11, 13, 14). The gene discussed is BPI; the disease is juvenile polyposis syndrome.