Supplementary Material for: Histologic Features of Secondary Syphilis

Background: Secondary syphilis is a sexually transmitted infection, which is referred to as “the great imitator” and has a wide spectrum of clinical manifestations. As a result, it is essential to identify potential secondary syphilis patients with ambiguous clinical manifestation through pathology. Objective: We sought to analyze the pathological features of secondary syphilis. Methods: We analyzed 59 biopsy specimens from 56 patients with secondary syphilis. Cases were classified according to the histological characteristics and clinical features. Results: Necrotic keratinocytes could be observed in 39 of 59 (66.1%) secondary specimens. Plasma cells (86.4%) were the most common finding overall. The presence of Treponema pallidum was detected mostly at the dermal-epidermal junction. There was no statistical significance between pathological features and age, HIV status, or RPR titer. Conclusions: Necrotic keratinocytes are one of the characteristics of secondary syphilis. The combination of plasma cells, irregular acanthosis, elongated rete ridges, and endothelial swelling should increase the likelihood of syphilis.