Necrotising fasciitis (NF) - emergency medicine revision
Overview
Necrotising fasciitis is a fulminant, life‑threatening infection that spreads rapidly along fascial planes, causing widespread necrosis of fascia and often overlying skin and underlying muscle.
It is a surgical emergency: early recognition, aggressive resuscitation, immediate broad‑spectrum IV antibiotics and urgent surgical debridement are essential. Diagnosis is primarily clinical; investigations and imaging are supportive but must not delay definitive surgical management when clinical suspicion is high (GOV.UK; RCEM).
Why NF is so severe
- Infection advances quickly in relatively avascular fascial planes, allowing organisms and toxins to extend beyond visible skin change.
- Toxin production (notably from Group A Streptococcus) causes local ischaemia and systemic toxicity (including streptococcal toxic shock syndrome).
- Polymicrobial synergism (aerobes + anaerobes, gas‑forming organisms) accelerates tissue destruction.
- The combination of rapid local destruction and systemic inflammatory response explains the high morbidity and mortality.
Microbiology and special variants
- Common organisms:
- Group A Streptococcus (Streptococcus pyogenes) is a frequent cause.
- Staphylococcus aureus (including MRSA) and clostridia may cause monomicrobial NF.
- Polymicrobial infections:
- Mixed Gram‑negative and Gram‑positive organisms with anaerobes are common, especially from perineal or abdominal sources; these may be gas‑forming.