A 28-year-old white man presented to the Emergency Department with a 24-hour history of an eruption on his extremities, trunk, and face. The patient was known to be HIV positive with a CD4 count of 527 and a viral load of 20,300. He denied fever, chills, malaise, and headache. His social history was significant for the fact that he was in a monogamous homosexual relationship. He had no recent travel, pet exposures, or sick contacts. Physical examination revealed stable vital signs and no documented fever. A maculopapular eruption was present on his face, trunk, and extremities (Figures 1 and 2). There was no palmar or plantar involvement. He was treated with diphenhydramine and topical 2.5% hydrocortisone and advised to return if his condition did not improve. Twelve days after the initial evaluation, the patient consulted us again due to progression of his dermatitis. He had no additional complaints other than an eruption on both palms but neither sole. (Figure 3). The eruption now demonstrated erythematous pink-red oval macules and papules 1-2 cm in size distributed on his scalp, face, trunk, and arms. A few papules contained fine collarettes of scale. Further questioning revealed that the patient had experienced a tender rectal ulcer 2 months previously. A punch biopsy and rapid plasma reagin were performed. The histopathologic examination revealed interface dermatitis with lymphocytes, plasma cells, occasional neutrophils, and a prominent lymphoplasmacytic perivascular dermatitis with infiltration of the vessel walls. Warthrin-Starry and Steiner methods demonstrated spirochetes at the dermal-epidermal junction and in vessel walls, consistent with Treponema pallidum (Figure 4). Rapid plasma reagin and fluorescent Treponema antibody were both reactive with a Venereal Disease Research Laboratory (VDRL) of 1:16. The patient was diagnosed as having secondary syphilis and treated with 2.4 million units of IM benzathine penicillin for 3 weeks. His eruption resolved after the initial treatment and he did not experience a Jarisch-Herxheimer reaction.