Treponema pallidum in peripheral nerve tissue of syphilitic chancres

Biopsies for electron microscopy were obtained from syphilitic chancres of 7 patients, 6 males and one female. In 4 of the patients, Treponemata pallida were seen gathering around peripheral nerves and invading the spaces between Schwann cells and their basal lamina. No definite degenerative changes were seen in the axons. In all patients, Treponemata pallida were gathering around the small blood vessels. The fine structure of Treponema pallidum in the lesions included a twined cytoplasmic cylinder with an inner and an outer lamina, an axial fibril consisting of three to five parallel filaments, each consisting of six microtubules, and a covering, outpouching periplastic membrane.