Malignant Syphilis: An Early Feature of Underlying HIV Infection in an MSM Patient

Introduction: Co-infection of human immunodeficiency virus (HIV) with syphilis is common and has significant clinical consequences. HIV infection can change the course and clinical manifestations of syphilis, resulting in atypical syphilis. A rare feature of this infection is malignant syphilis, which frequently resembles other skin lesions and poses a challenge in diagnosis. This report aims to describe a case of malignant syphilis in an HIV-positive patient. Case report: A 33-year-old man who has sex with men (MSM) came to the dermato-venereology outpatient clinic with chief complaints of ulcerative lesions on the face, trunk, arms, palms, and legs for the past two months. The patient complained of fever, chills, and decreased appetite two weeks prior to presentation. A dermatological examination showed numerous well-demarcated ulcerated plaques and nodules partially covered with crust. Reactive results were found on syphilis serologic tests with high titers. The test for HIV was reactive, with a CD4 cell count of 219 cells/mm³. The patient was then diagnosed with malignant syphilis and received treatment in the form of benzathine penicillin injection 2.4 million units once a week for three consecutive weeks. After treatment, the skin lesions and syphilis serologic titer improved. Conclusions: Secondary syphilis in patients with HIV infection may present as an atypical variant. As reported in this case, malignant syphilis should always be considered in the differential diagnosis when ulcerative and necrotic lesions are observed in individuals with HIV infection.