Treponema pallidum in leukoderma syphiliticum demonstrated by electron microscopy.

Punch biopsies from syphilitic leukoderma lesions and from unaffected skin in 3 patients with secondary syphilis were studies in the transmission electron microscope. In one of the patients the pigment disorder was not preceded by any visible syphilids, and in the biopsy from the leukodermal skin in this patient Treponemata pallidium were demonstrated around vessels and inside nerve fibres in which the myelin sheaths of the axons showed evidence of degeneration. In the other 2 patients the depigmented areas appeared while macular and papular syphilitic lesions were healing. In the biopsies from the leukodermal lesions of these 2 patients and from unaffected skin of all 3 patients, no treponemes were demonstrated. The study indicates that syphilitic leukoderma is not invariably a post-inflammatory phenomenon, but the pigmented skin lesions may themselves represent stigmata of an active syphilitic infection.