Kissing chancre of primary syphilis

A 30-year-old heterosexual man presented with a painless erosion lesion on the coronal sulcus for 3 weeks. It was oval, indurated, slightly elevated kissing erosion with clean, smooth bases (Fig. 1). The lesion in the prepuce, being too hard to bend, would flip over all at once when the prepuce was drawn back (dory flop phenomenon). He was otherwise asymptomatic, and the inguinal lymph nodes on both sides were not enlarged. The patient’s history revealed unprotected sexual intercourse with a female partner 5 weeks before the onset of the lesion. Direct immunofluorescence from the lesion confirmed the presence of treponema pallidum (Fig. 2). A rapid plasma reagin (RPR) test was positive, with a titer of 1:4. In addition, a T. pallidum particle agglutination assay was reactive, and a fluorescent treponemal antibody absorption test was reactive for both IgG and IgM antibodies. Serologic analysis for human immunodeficiency virus was negative. Primary syphilis was diagnosed and the patient received benzathine penicillin G and the lesion resolved within 5 weeks (Fig. 3). The kissing chancre refers to an ulcer occurring in a fold of the skin or mucous membrane which forms symmetrical lesions on each side. Locations for such ulcers can be on the lips, labia minora and coronal sulcus. The mechanism of kissing chancre is not clear, however, it is assumed that the ulcer is formed when one side of the skin or mucous membrane becomes infected and then autoinfects the other sided from prolonged close contact. Here, we report a kissing chancre on coronal sulcus. The differential diagnosis of kissing chancre should include genital herpes, chancroid, lymphogranuloma venereum, drug eruption, superficial fungal infection, traumatic injury and lichen planus. Herpetic ulcer should be multiple, painful and superficial, blisters occur at early stage, but atypical lesions may be difficult to