Culture-negative necrotizing soft tissue infection presenting as rapidly progressive sepsis in a previously healthy adolescent without trauma: a case report

Necrotizing soft tissue infection (NSTI) is a life-threatening condition requiring early recognition and prompt surgical intervention. Although classically associated with diabetes, immunosuppression, or trauma, NSTI may also occur in previously healthy adolescents, making early diagnosis particularly challenging. Early clinical manifestations are often subtle, misleading and nonspecific, while laboratory and imaging findings may remain non-diagnostic during the early stage of disease. We report a previously healthy adolescent male presenting with rapidly progressive sepsis of unclear origin following misleading early manifestations, including pharyngolaryngeal symptoms and disproportionate right lower limb pain despite initially subtle local findings. Initial evaluation at a referring hospital demonstrated severe systemic inflammation without an identifiable infectious focus. Despite broad-spectrum antimicrobial therapy, systemic toxicity progressed with early multiorgan involvement. Serial examinations revealed evolving disproportionate limb pain and swelling, while computed tomography demonstrated deep soft tissue edema without gas or abscess. Approximately 10 h after emergency department presentation, emergent diagnostic surgical exploration demonstrated severe soft tissue infection with partial subcutaneous necrosis and viable fascia, findings most compatible with an early necrotizing soft tissue infection without established fascial necrosis. Blood cultures and intraoperative subcutaneous fluid culture remained negative following antecedent broad-spectrum antimicrobial therapy. Prompt surgical source control combined with multidisciplinary antimicrobial management resulted in complete clinical recovery. This case highlights the diagnostic challenges of a suspected early necrotizing soft tissue infection without established fascial necrosis in a previously healthy adolescent presenting with culture-negative sepsis and non-localizing investigations. Disproportionate limb pain should be recognized as an important early clinical warning sign, particularly when accompanied by rapidly progressive systemic toxicity despite initially subtle local findings. Serial comprehensive physical examination and ongoing clinical reassessment remain fundamental to early recognition. When clinical suspicion persists despite inconclusive laboratory, microbiological, and imaging findings, timely diagnostic surgical exploration should not be delayed, as it provides direct assessment of tissue viability while enabling prompt source control.