could not identify a cut-off value for serum CXCL13 concentrations to differentiate between neurosyphilis and other infectious (viral and cryptococcal) and non-infections central nervous system (CNS) pathology, but the CSF CXCL13 levels were markedly increased in the neurosyphilis group compared with the other groups (25). The gene discussed is CXCL13; the disease is neurosyphilis.