Exploring the granulomatous manifestations of secondary syphilis: A case report.

Syphilis, caused by Treponema pallidum, progresses through distinct stages, with secondary syphilis often being the first presentation within 6-11 weeks after exposure. Although referred to as the "great mimicker", secondary syphilis has typical clinic and histopathological features. This report presents a case of secondary syphilis with absent palmoplantar involvement and unusual granulomatous pathological manifestations. Our patient presented with a diffuse headache and a spreading non-pruritic rash, which progressed to involve the chest, abdomen, upper extremities, and face. Diagnostic workup, including serology and biopsy, confirmed secondary syphilis with granulomatous inflammation. Histopathological examination revealed vacuolar interface dermatitis, neutrophilic mounds, and granulomatous inflammation, while a Treponema pallidum immunohistochemical stain identified spirochetes located primarily in the dermis. This case, representing the earliest documented instance of secondary granulomatous syphilis, challenges the typical association of granulomatous inflammation with tertiary syphilis and delayed hypersensitivity reactions. Instead, we propose that granuloma formation and the lack of palmoplantar involvement are an interrelated phenomena that occur concurrently in this rare subtype of secondary syphilis. We hypothesize that the sparing of the palms and soles, areas with thickened epidermis, may indicate a dermal-based granulomatous response. The patient responded well to IV penicillin therapy, highlighting the importance of early detection and treatment in managing syphilis with atypical histopathological features. With the recent increase in syphilis cases, this highlights the importance of recognizing both clinical and histopathological changes for prompt diagnosis and treatment.