Fatal soft-tissue and bony complications following radiotherapy for HIV-negative Kaposi's sarcoma: a rare case of post-radiation necrotizing fasciitis and osteomyelitis in a resource-limited setting.

Background: Kaposi's sarcoma (KS) is a vascular neoplasm strongly associated with HIV infection; however, HIV-negative KS is exceptionally rare, particularly in sub-Saharan Africa. Radiotherapy (RT) remains a standard local treatment for KS, providing excellent symptom relief and local control. Despite its efficacy, severe complications such as necrotizing fasciitis (NF) and osteomyelitis are exceedingly uncommon and scarcely reported in HIV-negative patients. Case Presentation: We report a 47-year-old HIV-negative man with biopsy-confirmed KS of the right thigh, initially treated with chemotherapy followed by external beam RT. Two months post-RT, he developed painful blistering lesions that progressed into extensive necrotic ulceration with foul discharge, fever, and progressive loss of limb function. Despite broad-spectrum antibiotics and multiple surgical debridements, recurrent necrosis persisted with poor granulation. Imaging and intraoperative findings confirmed femoral osteomyelitis with extensive destruction of periarticular soft tissues, tendons, and ligaments, resulting in a nonfunctional knee. The wound was too devitalized for grafting or flap reconstruction. Following multidisciplinary deliberation, above-knee amputation was performed as definitive salvage. Discussion: This case highlights a rare yet devastating iatrogenic complication post-RT NF with osteomyelitis in an HIV-negative KS patient. Distinguishing infection from radiation necrosis or tumor recurrence posed major diagnostic challenges. Radiation-induced obliterative microangiopathy and fibrosis likely predisposed the tissues to infection and impaired healing. Conclusion: Vigilant post-RT monitoring, prompt recognition of soft-tissue infection, aggressive multidisciplinary management, and timely radical surgery are essential. In resource-limited settings, limb salvage may be impossible, making amputation the only viable life-saving option.