Necrotizing fasciitis
Also called flesh-eating infection, necrotising soft tissue infection
Infection racing along the fascial plane beneath deceptively quiet skin. The examination finding that matters is a mismatch: pain and systemic toxicity far beyond what the surface shows. It is a surgical diagnosis, and every hour of hesitation is tissue.
How it looks
A rapidly advancing, exquisitely tender, dusky and indurated area with ill-defined margins, haemorrhagic bullae, and disproportionate systemic toxicity.
Rose is the lesion, grey the pattern the lesions make, green where on the body it lives.
Across skin tones
The early dusky-grey discoloration is far harder to appreciate in deeply pigmented skin, which delays recognition; disproportionate pain, woody induration, crepitus, bullae, and toxicity must carry the diagnosis without waiting for a colour change.
Don't miss
Marking the margin and reviewing in four hours is how this diagnosis is missed; if necrotizing infection crosses your mind, the next call is surgical, not a repeat examination.
Symptoms & course
- Pain out of proportion, then anaesthesia as nerves die
- Hour-by-hour spread beyond marked margins
- Fever, confusion, hypotension
Diagnostic approach
- None may delay surgery: the diagnosis is made in theatre
- Imaging and labs (LRINEC-type markers) only alongside, never gatekeeping
- Blood cultures and broad resuscitation in parallel
Differential, and how to separate them
- Cellulitis
Favours it: A spreading hot red tender limb
Against it: Cellulitis hurts in proportion, respects hours-to-days tempo, and has no crepitus, bullae, or skin anaesthesia
Management principles
- Immediate surgical exploration and radical debridement
- Broad-spectrum antibiotics including toxin suppression
- ICU-level resuscitation; repeat-look surgery is the rule
Clinical pearl: The patient who cannot bear the sheet touching a modestly red leg is telling you the disease is in the fascia, not the skin.
Keep going
Try the case: The leg that hurts more than it looksBack to the Atlas