Reflectance confocal microscopy for the in vivo detection of Treponema pallidum in skin lesions of secondary syphilis

BackgroundSecondary syphilis is a diagnostic challenge that relies on microscopic and laboratory tests.ObjectiveWe sought to assess the usefulness of in vivo reflectance confocal microscopy (RCM) to detect Treponema pallidum in lesions suggestive of secondary syphilis.MethodsMacular and papular skin lesions from 3 patients clinically suggestive of secondary syphilis were imaged by RCM and confirmed by skin punch biopsy.ResultsIn all lesions RCM demonstrated elongated small bright particles with a spiral shape intermingled with the keratinocytes. These features corresponded with immunohistochemical findings that revealed several spirochetes infiltrating the epidermis.LimitationsUnlike immunohistochemistry, RCM did not visualize T pallidum in the dermis and vascular walls because of limited imaging depth. The specificity and sensitivity of this technique need to be assessed.ConclusionRCM may be an effective diagnostic tool for in vivo real-time imaging of T pallidum in skin lesions of secondary syphilis, and seems to correlate well with immunohistochemistry.