[Granulomatous secondary syphilis; an uncommon presentation of a polymorphic disease].

Background: Due to a great diversity of clinical presentations secondary syphilis can mimic various skin diseases, which means that the diagnosis of this sexually transmitted condition can be missed. Occurrence of a granulomatous inflammatory reaction in secondary syphilis is rare and may be confused with other granulomatous dermatoses.

Case Description: We present a 37-year-old homosexual male with a granulomatous dermatitis due to secondary syphilis. The differential diagnosis based on clinical and histopathological findings was lengthy and the initial syphilitic serology results were negative, resulting in delayed diagnosis. After revision of the histopathology and repeated serological testing secondary syphilis could be diagnosed.

Conclusion: Not only the clinical, but also the histopathological presentation of secondary syphilis is variable. To prevent transmission, treatment delay and complications, we recommend repeating syphilitic serology following negative results if there is clinical or histopathological suspicion of this disease, especially in patients displaying high-risk behaviour. Syphilis should be also excluded in granulomatous dermatoses with plasma cells.