This patient appears to have primary syphilis, as evidenced by a penile chancre that was not tender. One ofthe differences between syphilis and herpes simplex virus (HSV) is that an HSV lesion is excruciatingly painful. Treponemal organisms may be seen microscopically in the lesion if the lesion is scraped. If not treated, the chancre will disappear and the patient will be asymptomatic until he/she exhibits the signs/symptoms of secondary syphilis, which include a disseminated rash and systemic involvement such as meningitis, hepatitis, or nephritis. There are two kinds of tests for the detection of syphilis antibodies: non- specific tests such as the RPR and VORL, and specific tests such as the FT A, TPHA (T pallidum hemagglutination test), and the MHTP (microhemagglutination-T pallidum). The difference is that the nonspecific tests use a cross- reactive antigen known as cardiolipin, while the specific tests use a T pallidum antigen. Although the nonspecific tests are sensitive, they lack specificity and often cross- react in patients who have diabetes, hepatitis, or infectious mononucleosis, or who are pregnant. Some patients, especially those with autoimmune diseases, will have both nonspecific (RPR) and specific tests (FTA) positive even if they do not have syphilis. Resolution of such a situation can be done by molecular methods for T pallidum, such as PCR, or by the immobilization test using live spirochetes and the patient's serum. In the TPI test, the spirochetes will die in the presence of specific antibody.