Necrotizing fasciitis vs Cellulitis
How to tell Necrotizing fasciitis and Cellulitis apart when a board question makes them look alike.
Nec fasc is toxic, fast, deep, and surgical; cellulitis is superficial soft-tissue infection treated medically unless abscess/complication appears.
Side by side
Necrotizing fasciitis is rapidly progressive deep fascial infection with pain out of proportion, systemic toxicity, bullae, skin anesthesia, crepitus, necrosis, shock, and need for emergent surgical debridement.
Cellulitis is bacterial infection of dermis/subcutaneous tissue with warmth, erythema, swelling, tenderness, and less sharply demarcated borders without fascial necrosis.
Polymicrobial infection or group A strep/S. aureus can spread along fascia, causing thrombosis, ischemia, and tissue necrosis.
Skin barrier disruption allows bacterial invasion of deeper dermis and subcutaneous tissue without the fulminant fascial destruction of necrotizing infection.
Severe pain, fever, hypotension, high CRP, hyponatremia, gas on imaging, gray dishwater fluid, and operative fascial necrosis support necrotizing fasciitis.
Localized warmth, erythema, edema, tenderness, lymphangitis, and improvement with antibiotics support cellulitis.
The trap
Early necrotizing fasciitis can look like cellulitis, so pain out of proportion and systemic toxicity should override benign skin appearance.
Watch it explained
Test it nowThe repair move
For red swollen skin, look for deep pain, speed, toxicity, anesthesia, bullae, gas, and shock.
Try a free question
CoreA patient has rapidly spreading leg erythema after a cut, severe pain out of proportion, fever, hypotension, bullae, skin anesthesia, and crepitus. Which diagnosis is most likely?
Show answer and explanation
Answer: A. Necrotizing fasciitis. Rapid progression with pain out of proportion, toxicity, bullae, anesthesia, crepitus, and shock supports necrotizing fasciitis.
Why the other choices are tempting
- B. Cellulitis is usually less toxic and lacks fascial necrosis signs.
- C. Erysipelas is superficial and sharply demarcated.
- D. Contact dermatitis is pruritic inflammatory dermatitis, not shock with crepitus.
- E. Stasis dermatitis is chronic venous inflammation.
Flashcards
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What pain clue supports necrotizing fasciitis?
Pain out of proportion supports necrotizing fasciitis.
What treatment is essential for necrotizing fasciitis?
Emergent surgical debridement plus broad antibiotics is essential.
Quick answers
What is the fastest way to tell Necrotizing fasciitis from Cellulitis?
Nec fasc is toxic, fast, deep, and surgical; cellulitis is superficial soft-tissue infection treated medically unless abscess/complication appears.
What is the key clue for Necrotizing fasciitis?
Necrotizing fasciitis is rapidly progressive deep fascial infection with pain out of proportion, systemic toxicity, bullae, skin anesthesia, crepitus, necrosis, shock, and need for emergent surgical debridement.
What is the key clue for Cellulitis?
Cellulitis is bacterial infection of dermis/subcutaneous tissue with warmth, erythema, swelling, tenderness, and less sharply demarcated borders without fascial necrosis.
What is the common trap with Necrotizing fasciitis vs Cellulitis?
Early necrotizing fasciitis can look like cellulitis, so pain out of proportion and systemic toxicity should override benign skin appearance.