Signs and Symptoms of Necrotizing Fasciitis
The most critical diagnostic feature of necrotizing fasciitis is severe pain that is disproportionate to the physical examination findings, which should immediately raise suspicion for this life-threatening infection. 1, 2, 3
Cardinal Clinical Features
Local Signs (in order of diagnostic importance)
Pain out of proportion to physical findings is the hallmark early symptom and occurs in approximately 75% of cases, often before other signs become apparent 1, 3, 4
Hard, wooden feel of subcutaneous tissue extending beyond the area of apparent skin involvement distinguishes necrotizing fasciitis from simple cellulitis, where tissues remain soft and palpable 1, 3
Edema or tenderness extending beyond the cutaneous erythema is present in approximately 80% of cases and represents a critical diagnostic feature indicating deeper tissue involvement 1, 3
Skin changes progress in a characteristic pattern: initially pale, then mottled and purple, and finally gangrenous, with skin necrosis or ecchymoses present in 70% of cases 1, 3, 5
Bullous lesions (fluid-filled blisters) develop as the infection progresses and are present in a significant proportion of cases 1, 3, 4
Crepitus (crackling sensation under the skin) indicates gas in the tissues and is a highly specific finding, though it is only present in a minority of cases and typically absent in pure aerobic infections like those caused by Streptococcus pyogenes 1, 2, 3
Erythema (redness) occurs in 90% of cases but is less diagnostically useful since it is also common in simple cellulitis 3
Systemic Signs
Fever is a common systemic manifestation of the toxin-mediated inflammatory response 1
Tachycardia (rapid heart rate) develops as part of the systemic inflammatory response 1
Hypotension and shock occur as the infection progresses and toxins are absorbed into the bloodstream 1
Altered mental status is a critical indicator of systemic toxicity and should prompt immediate surgical consultation 1, 3
Signs of organ dysfunction may develop as the massive release of cytokines produces an uncontrolled systemic inflammatory response leading to multisystem organ failure 1
Clinical Course and Progression
Failure to respond to initial antibiotic therapy within 24-48 hours is a critical red flag that should prompt immediate surgical exploration 1, 2, 3
Rapid progression is characteristic, with the clinical picture potentially worsening within hours, not days 1
Local pain may be replaced by numbness or analgesia as the disease progresses and nerves become involved, which paradoxically indicates worsening infection 5
Critical Diagnostic Pitfalls
Early diagnosis is missed or delayed in 85-100% of cases because the overlying cutaneous inflammation may initially resemble simple cellulitis, and there is a paucity of specific skin findings early in the disease 1, 6, 7
The diagnosis is primarily clinical and requires a high index of suspicion, as laboratory tests and imaging are not highly sensitive or specific 1, 3
Do not wait for imaging confirmation when clinical suspicion exists, as imaging studies should never delay surgical consultation and intervention 1, 2
The LRINEC score lacks sensitivity for early diagnosis and should not be relied upon to rule out necrotizing fasciitis 1