The co-infection of syphilis and HIV is not well understood, but a decreased of CD4 counts and enhanced viral load in an HIV-infected population has been reported in patients with syphilis.32,33 Furthermore, RPR and treponemal test have shown false-positive and false-negative results, and syphilis results need to be regarded with caution in a HIV endemic setting. The gene discussed is CD4; the disease is coinfection.