Clinical signs of infections may be absent or vague in a wide percentage of patients, serum inflammatory markers (i.e., erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP)) demonstrated a quite low specificity and accuracy in the diagnosis of PJI, therefore, the diagnosis relies on a combination of clinical, biological and microbiological findings, the latter comprising periprosthetic cultures obtained on preoperative synovial fluid and/or intraoperative tissues [11,12,13,14]. The gene discussed is CRP; the disease is juvenile polyposis syndrome.