Fulminant ulceronecrotic dermatosis: revisiting a classic diagnosis

Malignant syphilis (lues maligna) is a rare and aggressive variant of secondary syphilis, predominantly affecting immunocompromised patients. We report a 56-year-old male with newly diagnosed human immunodeficiency virus (HIV)-1 infection (viral load 637,000 copies/mL; CD4+ 134 cells/μL) who presented with a 1-2-month history of constitutional symptoms followed by a fulminant, disseminated ulceronecrotic dermatosis involving the scalp, face, trunk and limbs. A vesicular eruption preceding the ulceronecrotic phase was initially misdiagnosed as varicella. Diagnosis was established on the integration of clinical findings, serological confirmation (rapid plasma reagin 1:16; positive Treponema pallidum antibody), positive DNA polymerase chain reaction for T. pallidum from a cutaneous ulcer exudate, and compatible skin biopsy histology. The patient was treated with three weekly doses of intramuscular benzathine penicillin G 2.4 million units, with complete healing and only atrophic scarring at 4-month follow-up. This case highlights that malignant syphilis can manifest as a rapidly progressive ulceronecrotic dermatosis,and underscores the importance of maintaining a broad differential diagnosis in the context of newly diagnosed HIV infection.