A 22-year-old man presented with a three-week history of an indurated, mildly painful erythematous plaque on the balanoprepucial groove (Fig. 1). Non-tender inguinal lymphadenopathies were present. He reported unprotected sex four weeks before. Serological tests for syphilis revealed a positive RPR test (1:8) and a reactive TPHA test.

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