An Atypical Solitary Lesion: Secondary Syphilis, The Great Imitator

Although dermoscopy can support the diagnosis of several inflammatory and infectious diseases, its use is less common in general dermatology due to the lack of specific criteria and the great dermoscopic expertise of a specialist required for correct diagnosis. Observation: Here we report the case of a 69-year-old hepatitis C positive MSM patient, who was admitted to our department due to a solitary firm painless erythematous maculopapular lesion with a central crater-like crust on the upper right thigh that occurred two months prior. The dermoscopy showed an erythematous, copper-colored, oval lesion with diffuse monomorphic dotted and glomerular vessels, central crust, and circular scaling (Biett’s sign). The histological findings ruled out neoplasia and described a plasma cell infiltrate and endothelial swelling. Finally, the combination of the dermoscopic image, histological findings and the additionally acquired knowledge about the sexual history of the patient at the second visit led to the diagnosis, which was then confirmed with serological tests. Key message: Dermoscopy may become a supportive tool to facilitate the recognition of secondary syphilis, however, the reporting of these atypical cases is crucial to highlight the many faces of the disease, so clinicians consider syphilis as part of the differential diagnosis of non-specific lesions.