28 Sept 2026 · Case #023
Necrotizing fasciitis
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Diagnosis
Necrotizing fasciitis
First-line treatment
Immediate radical surgical debridement with broad-spectrum antibiotics
How the diagnosis is reached
Pain grossly out of proportion to visible skin changes, in a septic diabetic patient with a rapidly advancing margin, is necrotizing fasciitis until surgically disproven. Several features separate it from simple cellulitis: the woody induration extending past the erythema, patchy anaesthesia from destruction of cutaneous nerves as infection tracks along the fascial plane, crepitus, haemorrhagic bullae, and systemic toxicity out of keeping with the visible lesion. The laboratory picture is captured by the LRINEC score (leukocytosis, high CRP, hyponatremia, raised creatinine and hyperglycemia) though a low score never excludes the diagnosis and should not reassure. Soft tissue gas on plain film is highly suggestive but present in only a minority. The single most important point is that this is a clinical diagnosis requiring immediate exploration: CT or MRI may support it, but arranging them delays the only intervention that alters outcome. Diabetes is the commonest predisposing condition, and infection is usually polymicrobial, though group A Streptococcus causes the fulminant monomicrobial form. Treatment is the operation and everything else is adjunct: radical debridement back to bleeding, healthy tissue is at once the diagnostic test and the cure, and a creatine kinase of 1860 U/L says the necrosis already involves muscle, so the exploration must go deeper than fascia. Broad-spectrum cover for Gram-positives, Gram-negatives and anaerobes runs alongside, with clindamycin added specifically because it suppresses streptococcal exotoxin production rather than merely killing the organism. Repeat debridement at 24 hours is the rule rather than the exception. The urgency is quantifiable: mortality roughly doubles for every 12 hours surgery is delayed, and with a blood pressure of 94/56 and a margin moving 4 cm in three hours, those hours are already being spent.
Key clinical clues
- Pain far exceeding the visible skin changes, with woody induration beyond the erythema
- Patchy anaesthesia over the affected skin and palpable crepitus
- Erythema margin advancing 4 cm in three hours, with haemorrhagic bullae
- Hyponatremia, leukocytosis, raised CRP and creatinine in a hyperglycemic diabetic
- Soft tissue gas on plain radiograph, go to theatre, do not arrange more imaging
The case in full
Presenting complaint
Patient history
A 55-year-old man with type 2 diabetes presents with 24 hours of rapidly worsening left foot pain. He caught his heel on a garden step two days ago, breaking the skin. He describes the pain as the worst of his life.
Examination
Physical examination
There is a 3 cm graze over the heel with dusky, ill-defined erythema extending well beyond it, and a tense, woody hindfoot. Palpation causes pain far exceeding the skin appearance, with fine crackling under the fingertips. Sensation is patchy.
Observations
Vital signs
Observations are recorded in triage.
| Parameter | Value | Reference |
|---|---|---|
| Temperature | 38.9 °CRef 36.1–37.5 | 36.1–37.5 |
| Heart rate | 126 bpmRef 60–100 | 60–100 |
| Blood pressure | 94/56 mmHg | – |
| Respiratory rate | 26 /minRef 12–20 | 12–20 |
Laboratory results
Laboratory results
Bloods are sent urgently.
| Parameter | Value | Reference |
|---|---|---|
| White blood cells | 27.8 ×10⁹/LRef 4.5–11.0 | 4.5–11.0 |
| C-reactive protein | 284 mg/LRef <5 | <5 |
| Sodium | 128 mmol/LRef 135–145 | 135–145 |
| Creatinine | 2.2 mg/dLRef 0.7–1.3 | 0.7–1.3 |
| Glucose | 268 mg/dLRef 70–110 | 70–110 |
| Creatine kinase | 1860 U/LRef 30–200 | 30–200 |
| Lactate | 3.8 mmol/LRef 0.5–2.2 | 0.5–2.2 |
Progression
Clinical course
The leading edge of the erythema was marked on arrival. Three hours later it has advanced 4 cm proximally past the ankle, and two flaccid haemorrhagic blisters have appeared over the hindfoot.
Imaging
Imaging
A plain radiograph of the foot and ankle is obtained at the bedside. Fine streaks of gas track through the soft tissues along the deep fascial planes, well beyond the area of visible skin change, and the bones themselves are intact. The surgical registrar is called before any further imaging is arranged.