Chancroid: Haemophilus ducreyi causes these ulcers and is usually associated with suppurative inguinal lymphadenopathy. & Genital herpes: HSV type 1 or type 2 causes multiple vesicular or ulcerative painful genital ulcers, often associated with inguinal lymphadenopathy. HSV-2 is classically associated with this presentation, but HSV-1 may be causative in up to 50% of cases. & Granuloma inguinale: Klebsiella granulomatis (formerly Calymmatobacterium granulomatis) causes painless, genital ulcerative disease. The lesions are highly vascular, bleed easily on contact, and rarely occur in the United States. & LGV: Chlamydia trachomatis serovars L1, L2, L3 causes tender inguinal or femoral lymphadenopathy that is typically unilater
Nontreponemal tests (reactive plasma reagin [RPR] and Venereal Disease Research Laboratory [VDRL]) are not specific for syphilis and can be falsely positive under many conditions. These tests are used to screen for syphilis and to assess therapeutic response because the titers return to normal over time after therapy is initiated. Treponemal tests are specific for syphilis and include the microhemagglutination assay for Treponema pallidum
