Secondary syphilis mimicking pemphigus vulgaris

Syphilis is an infective sexually transmitted disease, caused by an anaerobic filamentous spirochete, named Treponema Pallidum, which may be present in variable and different clinical forms. Over the last decade, this pathology has emerged in Western Europe with an unusual recrudescence, despite the well-known preventive measures, 1,2,3,4 probably due to easy of travel and loosening of national boundaries.5 We describe a case of a middle-age Caucasian woman with oral secondary syphilis, which clinically and immuno-histologically simulated a pemphigus vulgaris (PV). A 47 year-old woman was referred to our Oral Medicine Unit by her general practitioner for a desquamative gingivitis localized at the anterior lower teeth and for a bullous-erosive lesion localized at the right edge of the tongue. The Nikolsky’s sign was positive. Histology with haematoxylin/eosin revealed a suprabasal epithelial detachment with a prominent eosino-neutrophilic infiltrate, suggesting a possible PV. Direct immunofluorescence (DIF) showed positive for intercellular cement substance (ICS), with its classic “net-like” aspect. Indirect immunofluorescence using monkey oesophagus, and ELISA testing for Dsg1/3 and BP180/230 were negative. The diagnosis of PV was confirmed and the patient received 75 mg of prednisone daily. One week after commencing therapy, she developed rosy-circular papulosquamous lesions on the palms and soles, for which she was referred to a dermatologist, who suspected a diagnosis of secondary syphilis and, thus, recommended stopping the corticosteroids and performing the serological tests for syphilis. The venereal disease research laboratory (VDRL) test showed a titer of 1:1280, the treponema pallidum hemagglutinin assay (TPHA) showed strong positivity as did the IgG fluorescent treponemal antibody-absorption (FTA-abs) test. Histology from the skin biopsy revealed a suprabasal epithelial detachment with an abundant mixed inflammatory infiltrate in the underlying dermis, unlike the common histopathology of syphilis.6 Thus, the immuno-histochemistry (anti-CD 38) on the oral biopsy specimen was performed and revealed the presence of Treponema. After the diagnosis of secondary syphilis, she received 1.200.000 U.I. of benzylpenicillin benzathine twice a week and, four weeks later, all lesions healed. Syphilis is also known as “the great imitator”, due to its ability to present clinically multiform muco-cutaneous aspects. In the oral cavity, it may occur in all three stages and the two most common features of secondary syphilis are represented by maculopapular lesions and mucous patches, which may coalesce and give snail-track ulcers. Although oral ulcerations in secondary syphilis are rare findings, they have been described and may show as oval ulcers covered by a white or gray pseudomembrane. Our patient only had tongue ulceration, with an erythematous-erosive lesion of the lower gum. Such clinical features, supported by the immuno-histological findings of a suprabasal acantholysis with a strong positive IgG autoantibody signal against the ICS, and a positive C3C accumulation, led us to make an initial diagnosis of PV. Although the histological and clinical characteristics of secondary syphilis are somewhat variable, simulating different diseases, such as oral hairy leukoplakia, cutaneous eczema, nonetheless, to our knowledge, an acantholytic lesion with a positive DIF has never previously been described as a pattern of secondary syphilis. PV is an autoimmune muco-cutaneous blistering disease (AMBD), which, commonly, enters into the differential diagnosis with other autoimmune bullous diseases and not with infectious diseases, except the Herpes virus family. Thus, this case focuses on the probability of a possible serious misdiagnosis and, then, on the need to consider the AMBDs in the differential diagnosis of secondary syphilis. The routine serologic tests for syphilis are mandatory in all cases in which, during the therapy, the disease shows any curious abnormality, which might lie outside an AMBD.