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.