Case report We report the case of a 22 years old male patient, who presented with a vesicular eruption, bacterial over infected, with a group pattern distribution throughout the entire skin, evolving for approximately three months. The patient was previously treated for this condition with systemic antibiotics, which he could not mention, being diagnosed with superficial folliculitis. However, no improvement was noticed. He denied unprotected sexual intercourse. The patient was clinically examined and we performed routine tests, immunologic assays, bacteriological swab and skin biopsy. General examination showed generalized, painless micropoly-lymphadenopathy and continuous muscle pain in the lower legs. Dermatological assessment of lesions revealed a disseminated eruption on the entire skin, including the face and penis sheath, consisting of erythematous plaques with the surface covered by crusts and vesicles arranged in groups, with various sizes (diameter 13 cm) and clearly defined edges. The presumptive diagnosis was secondary syphilis, and in order to rule out the differential diagnosis of pityriasis lichenoides et varioliformis acuta, eosinophilic folliculitis and systemic lupus erythematosus we performed a series of tests including immunologic assays, viral markers for HCV, serology for syphilis, bacteriological swab from the lesions and a skin biopsy. The results were positive for syphilis and Staphylococcus aureus was isolated from the lesions. Histopathological appearance of psoriasiform and lichenoid dermatitis with plasma cells was interpreted in the context of secondary syphilis, confirming our diagnosis. The patient eventually admitted having multiple unprotected sexual contacts. We tested for HIV Ag/Ac (1 + 2), which was positive.