Solitary ulcer at the mons pubis in a heterosexual male patient

BACKGROUND: Syphilis is a curable, systemic sexually transmitted infection caused by the bacterium Treponema pallidum subsp. pallidum (TP). It is known as the "great imitator" due to its potential to mimic various dermatoses, possibly delaying correct diagnosis, particularly if syphilitic lesions appear in atypical locations. CASE DESCRIPTION: We report the case of a 54-year-old heterosexual white man who presented with a solitary, indurated ulcer on the mons pubis. Patient history revealed minimal trauma to the area 3 weeks prior, resulting from shaving. Initial topical treatment for bacterial folliculitis resulted in worsening of the lesion. Finally, in site polymerase chain reaction (PCR) for TP and syphilis serology verified the diagnosis of a chancre. CONCLUSION: This case underlines the importance of including syphilis in the differential diagnosis of any anogenital ulceration, even in uncommon anatomical sites and populations, thereby enabling prompt diagnosis and treatment.