Annular secondary syphilis with HIV coinfection that resembles other dermatoses

Syphilis is a sexually transmitted infection with manifestations that can mimic other diseases, leading to misdiagnosis. Annular syphilis is a rare atypical secondary syphilitic lesion that seldomly involves the face. Human immunodeficiency virus (HIV) coinfection can increasingly lead to atypical manifestations of syphilis and complicate the diagnosis. Herein, we describe a 29-year-old man with a diagnosis of annular secondary syphilis and HIV coinfection. He had clinical manifestations of annular erythematous papules and plaques with white scales at the edges, distributed and scattered on the face, neck, and upper back. The skin lesions went undetected on several visits and were misdiagnosed owing to similarities with other dermatoses. Serological examination showed positive Treponema pallidum particle agglutination assay and venereal disease research laboratory test titer 1/512, confirming syphilis infection. Results from the histopathological examination supported the diagnosis of secondary syphilis. Positive anti-HIV rapid test results indicated concurrent HIV infection. He was treated for syphilis and given antiretroviral therapy, and showed a good response as demonstrated by improvement of the lesions and serological titers. This case highlights the importance of recognizing the possibility of annular secondary syphilis and HIV coinfection which can have atypical manifestations.