What clinical features should I look for to differentiate necrotizing fasciitis from other soft tissue infections?

To differentiate necrotizing fasciitis (NF) from other soft tissue infections clinically, key features to look for include:

• Severe, rapidly progressing pain that is disproportionate to the visible skin changes, often described as deep, intense, and out of proportion to the apparent superficial infection.
• Early systemic toxicity such as fever, tachycardia, hypotension, and signs of sepsis, which are more pronounced than in typical cellulitis or abscess.
• Skin changes evolving quickly from erythema and swelling to dusky discoloration, blistering, bullae formation, and necrosis, indicating deeper tissue involvement.
• Crepitus or gas in tissues may be palpable or visible, suggesting gas-forming organisms, although this is not always present.
• Rapid progression of swelling and induration beyond the margins of erythema, often with tenderness extending deep along fascial planes rather than just the skin.
• Failure to respond to initial antibiotic therapy and worsening clinical signs despite treatment.
• Systemic signs of multi-organ involvement such as confusion or acute kidney injury may develop early.

These clinical features help distinguish NF from less severe soft tissue infections like cellulitis or abscess, which typically have more localized pain, slower progression, and less systemic toxicity. Imaging such as MRI can support diagnosis by showing fascial edema and fluid tracking along fascial planes, but clinical suspicion based on these features is critical for early diagnosis and urgent surgical referral ¹ (Ali et al., 2014; Hayeri et al., 2016; Pal et al., 2024).