Perivascular cuff and spread of Treponema pallidum.

BACKGROUND: The incidence of syphilis is on the rise in many cities worldwide. Both the clinical and histopathological changes do not always fulfil the typical diagnostic criteria. Immunohistochemistry is available to identify and localize Treponema pallidum. Two main patterns of T. pallidum distribution were described in the skin, namely heavy intraepidermal infiltration and scattered pattern inside the lichenoid cell infiltrate. OBJECTIVE: To search for a third pattern consistent with dissemination of the disease. METHODS: Immunohistochemistry using an antispirochete (T. pallidum and Borrelia) antibody was used in all cases of syphilis submitted to our laboratory. In addition, deposits of immunoglobulins and complement indicative of immune complexes were searched for. RESULTS: According to the cases, T. pallidum was disclosed in a combination of three patterns. The previously described epidermal and lichenoid patterns were confirmed, and a third pattern predominating in a perivascular location throughout the dermis was clearly identified in primary syphilis. The microorganisms were abundant in extracellular and intracellular locations, particularly inside endothelial cells. No deposits of immunoglobulins and complement were disclosed. CONCLUSION: The perivascular cuff of T. pallidum throughout the dermis might be representative of the dissemination phase of T. pallidum.