CD4 and syphilis: We assumed that the repetitive high-risk behavior resulted in syphilis re-infection frequently, and actually it is common among the HIV patients.6,21 It is well known that patients with any levels of CD4 cell count could get infected by T pallidum, presumably, the CD4 cell counts was not related to the diagnosis of syphilis or neurosyphilis.22 However, we were unable to explain the finding that CD4 <350 per μL was a predictor for neurosyphilis among all the co-infected patients with or without neurological symptoms.