Syphilitic mucous patches: the resurgence of an old classic

A 20-year-old woman was referred to our department for evaluation of multiple persistent erosive lesions of the oral mucosa that appeared 3 months before consultation. She complained of sore throat and a vague local discomfort. Her past medical history was unremarkable. Physical examination disclosed symmetrical erosive serpiginous hypertrophic plaques on the buccal commissures and buccal mucosa, whitish erythematous plaques on the tongue surface and erosions of the lips (Fig. 1). Enanthem and a few small vesicles on the soft palate were also observed. No similar mucocutaneous lesions were present elsewhere. The patient was otherwise in a good general status, with no fever or palpable enlarged lymph nodes. Two 4-mm punch biopsies were performed. Histopathological study showed irregular acanthosis with an intense, diffuse and perivascular infiltrate in the submucosa (Fig. 2). The cellular infiltrate consisted mainly of mature plasma cells. Polymorphonuclear leukocyte exocytosis with intraepithelial pustule formation was also observed, along with isolated apoptotic keratinocytes. A PAS stain failed to show any microorganisms and direct immunofluorescence study was negative. Immunohistochemical staining with a polyclonal rabbit antibody against Treponema pallidum revealed multiple spirochetes, mainly distributed in the lower layers of the mucosa, adopting a honey-comb pattern drawing the keratinocyte walls (Fig. 3). Microorganisms were also evident, although in a much weaker amount, within the infiltrate in the upper submucosa. Specific antitreponemal IgG and nontreponemal tests (VDRL, titre 1/256) were positive, with negative HIV-1/ 2 serology. The diagnosis of oral mucous patches (a form of secondary syphilis) was established, in the absence of other constitutional, genital, or skin manifestations. Treatment with benzathine penicillin (2.4 MU) was prescribed. The patient was lost for follow-up.