We present a 36-year-old HIV-positive man with a sixweek history of spreading, ulcerative, and necroticcutaneous lesions. Laboratory and histopathologicexamination revealed syphilis. This case of malignantsyphilis, also known as lues maligna, is an uncommonvariant of this sexually transmitted infection. This casehighlights the importance of including malignantsyphilis in the differential diagnosis of patientspresenting with a disseminated ulcerative andnecrotic rash, especially in individuals with HIV.