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.

A 40-year-old man reported a 5-day history of fever and malaise, followed by a pruritic generalized rash that started 1 month before initial medical consultation. He was sent to dermatology where he was diagnosed with post-streptococcal guttate psoriasis and a phototherapy treatment was initiated. After the third phototherapy session, fever and malaise reappeared and the patient was sent to the Emergency Department. On history, the male patient reported having sex with other men (MSM). Examination showed a febrile state (39.8°C), a generalized tender lymphadenopathy, and hepatosplenomegaly. He also had well-demarcated erythematous papules and plaques with scaling, some of them target-like, on the scalp, the trunk, the abdomen and the extremities with palmoplantar involvement (Fig. 1A). The patient was diagnosed with secondary syphilis based on a positive Treponema pallidum EIA and RPR (1:512). The skin biopsy showed a psoriasiform lichenoid dermatitis with plasma cells. The anti-T. pallidum antibody confirmed the presence of spirochetes, most numerous in the region of the epidermal basement membrane (Fig. 1B). He was also found to be HCV and HIV positive (CD4+ T-cell count: 360 cells/mm3).

Figure 1:

Rash of secondary syphilis. Annular erythematosquamous papules and plaques on the back (A), some of them target-like. Treponema pallidum spirochetes revealed by immunohistochemistery in the epidermal basal membrane and the superficial dermis (B).

This case illustrates why syphilis earned the name of the “Great Mimicker”. 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 [1]. Also, typical target lesions are most often associated with erythema multiforme, but they can rarely occur in secondary and congenital syphilis [2]. Palmoplantar lesions were a helpful finding as they suggest the possibility of secondary syphilis. This case emphasizes the importance of evaluating risk factors such as unprotected sexual exposure, especially in MSM. Syphilis should also 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.