Cutaneous lesions of secondary syphilis are highly infectious and can mimic many skin disorders, making the diagnosis more difficult. They typically present as generalized, nonpruritic erythematous-to-copper-colored macules and papules, characteristically involving palms and soles. In 80% of patients the rash develops insidiously. However, rare forms of secondary syphilis present as rapidly progressive papulopustular lesions. These forms of syphilis are usually associated with human immunodeficiency virus infection and immunosuppression. We report a case of secondary syphilis presenting with an acute, rapidly progressive purpuric eruption mimicking leukocytoclastic vasculitis. A 61-year-old man presented with a 6-day history of nonpruritic rash on his chest and lower extremities associated with fatigue, sore throat, and night sweats. Examination revealed purpuric papules, extending from the dorsal feet to the hips; mucosal surfaces were not involved. A diagnosis of cutaneous small-vessel vasculitis was favored with possible triggers of IgA vasculitis. Initial work-up showed acute kidney injury and microscopic hematuria. Renal biopsy showed IgA nephropathy with mesangioproliferative glomerulonephritis. The patient's rash progressed to cover almost his entire body sparing palms and soles. Skin biopsy showed heavy perivascular lymphoplasmacytic infiltrate, capillary endothelial cell swelling, and sparse perivascular neutrophilic nuclear dust. Spirochetal stain highlighted scattered epidermal and dermal organisms.
