Treponema Pallidum Epidermotropism in Nodular Secondary Syphilis

Nodular secondary syphilis results from the hematogenous and lymphatic dissemination of spirochetes. Clinically, the lesions appear as partially infiltrated plaques or red-violaceous nodules, which can be solitary or multiple. Several hypotheses have been put forward to explain the formation of these infiltrated or granulomatous lesions. Among the most accepted are the specific hypersensitivity reactions to Treponema pallidum or the lenghty duration of the disease. We present a case of nodular syphilis where immunohistochemistry revealed the presence of multiple spirochetes invading the epidermis.