Previous studies have shown that the CXCL13 concentration of the cerebral spinal fluid (CSF) in human immunodeficiency virus (HIV)-negative/positive patients with neurosyphilis is significantly higher than in patients without neurosyphilis and thus CSF CXCL13 may serve as a marker in the diagnosis of neurosyphilis [7,8,9]. The gene discussed is CXCL13; the disease is neurosyphilis.