Primary Syphilis Presenting As a Chronic Lip Ulcer.

Syphilis is usually a sexually transmitted infection caused by the spirochete Treponema pallidum. Primary syphilis classically presents as a painless, ulcerated lesion on the genitals. However, the primary lesion is not restricted to this site and appears wherever the spirochete enters through the skin. The symptomatology and appearance of the primary lesion can also vary.  We present a case of a 59-year-old man with a primary syphilitic chancre of the lower lip. The patient was referred to the dermatology clinic by their primary care provider after the ulceration failed to heal with antibiotic therapy. A biopsy of the lesion was taken at this time; the diagnosis of syphilis was then made by histologic examination and immunohistochemical staining. Subsequent serologic tests were also positive. Upon prompting, the patient did report a history of sexually transmitted disease but not of syphilis specifically. The patient was treated with penicillin, and there was clinical improvement of the lesion at the follow-up visit.