Abstract

Syphilis is notorious for its ability to present both clinically and histologically in a manner that closely mimics various dermatoses, making its diagnosis challenging. In this case report, we present a 50-year-old male patient with a six-month history of diffuse, erythematous, annular, non-scaly papules and plaques on his trunk, forearms, and proximal thighs. Initially treated as pityriasis rosacea by his primary care physician, the patient failed topical triamcinolone and oral antivirals. Upon referral to dermatology, two punch biopsies were performed, and the dermatologist’s clinical differential diagnosis included granuloma annulare, mycosis fungoides, pityriasis rosea and sarcoidosis. Histological examination revealed an unremarkable epidermis with moderately dense superficial and deep perivascular and peri-eccrine lymphoplasmacytic inflammatory infiltrates. Notably, marked dermal mucin deposition was also observed, leading to a preliminary diagnosis of tumid lupus. However, immunohistochemical staining readily identified numerous treponemal organisms, with subsequent serologic studies confirming a diagnosis of secondary syphilis. To our knowledge, reports describing secondary syphilis presenting with a tumid lupus-like histological pattern are limited in the literature. This case adds to the existing knowledge by emphasizing the potential overlap in histopathological features between these two entities. Given the escalating incidence of syphilis and the significant consequences associated with a missed or delayed diagnosis, dermatopathologists should remain vigilant and consider syphilis as a potential underlying cause in patients presenting with tumid lupus-like histology. Prompt recognition and appropriate management are essential to prevent disease progression, minimize complications, and curtail the spread of this reemerging sexually transmitted infection.