A case report and a review of the literature of the most common extragenital localization of primary syphilis

Syphilis is a chronic bacterial infection caused by Treponema pallidum and is schematically divided into 4 stages. Its primary form usually appears as an indolent ulcer called chancre, which spontaneously heals in 2-8 weeks. The most commonly affected site is the anogenital region, but extragenital lesions are also seen, especially in the oral cavity. In this study, we aimed to investigate this specific localization of the primary form. We present the case of a 62-year-old male with an unusual presentation of primary syphilis on the upper lip along with a review of the literature on primary syphilis of the oral cavity, reporting 32 patients. Oral primary syphilis may have unusual clinical features and may present as painful, multiple, or non-ulcerative lesions. This condition leads to a difficult differential diagnosis with many other infectious, neoplastic, and inflammatory conditions; owing to its transient nature and low symptomatology, it may also go unnoticed and reoccur in more advanced and dangerous stages. In conclusion, a primary treponemal infection must always be considered in the differential diagnosis of oral lesions of undetermined etiology, and proper investigation (with treponemal/non-treponemal tests and eventually a biopsy) should always be performed.