A secondary syphilis rash with scaly target lesions

A 40-year-old man reported a 5-day history of fever and malaise, followed by a pruritic generalized rash. He had well-demarcated erythematous papules and plaques with scaling. The patient was diagnosed with secondary syphilis. The skin biopsy showed a psoriasiform lichenoid dermatitis with plasma cells. The anti-T. pallidum antibody confirmed the presence of spirochetes. He was also found to be hepatitis C virus and human immunodeficiency virus positive. The characteristic rash of secondary syphilis may appear as maculopapular, evolving initially from macules to small reddish-brown papules with minor scaling later. When the scaling is prominent, lesions can be difficult to differentiate from guttate psoriasis. Typical target lesions are most often associated with erythema multiforme, but they can rarely occur in secondary and congenital syphilis. Syphilis should be suspected in high-risk patients presenting a variety of atypical syndromes such as neurologic symptoms, uveitis or cholestatic hepatitis, especially if palmoplantar lesions are present.