Unusual cutaneous features of syphilis in patients positive for human immunodeficiency virus

Dermatologists commonly find it difficult to diagnose syphilis, because of its protean clinical features. In cases of co-infection with human immunodeficiency virus (HIV) syphilis may present particularly unusual clinical features, further confounding the diagnosis. We report two cases of syphilis/HIV co-infection in Japanese patients showing uncommon skin features that made the diagnosis of syphilis difficult. These cases underline the need for dermatologists to be more aware of atypical cutaneous features of syphilis in patients positive for HIV.