Introduction

Necrotizing fasciitis is a rapidly progressive, life-threatening soft tissue infection characterized by extensive necrosis of the deep fascia, subcutaneous tissues, and surrounding soft tissues, with secondary involvement of the skin and underlying muscles. It is a true surgical emergency because the infection spreads rapidly along fascial planes, causing widespread tissue destruction, systemic toxicity, septic shock, multiorgan failure, and death if not recognized and treated promptly.

The condition is most commonly caused by Group A Streptococcus (Streptococcus pyogenes), either alone or in combination with other aerobic and anaerobic organisms. Early diagnosis, immediate broad-spectrum antimicrobial therapy, aggressive surgical debridement, and intensive supportive care are essential for survival.

Epidemiology

• Uncommon but associated with high morbidity and mortality.

• Mortality ranges from 20% to over 40%, depending on the timing of diagnosis and treatment.

• Occurs in all age groups but is more common in adults.

• Incidence is increasing because of ageing populations and increasing prevalence of diabetes mellitus and immunosuppression.

• Lower limbs are the most commonly affected anatomical site.

Classification

According to microbiology

Type I (polymicrobial)

• Most common form.

• Caused by mixed aerobic and anaerobic bacteria.

• Frequently occurs in patients with diabetes mellitus or peripheral vascular disease.

Type II (monomicrobial)

• Usually caused by Streptococcus pyogenes.

• May occur with or without Staphylococcus aureus.

Type III

• Caused by marine organisms such as Vibrio vulnificus or Gram-negative bacteria.

Type IV

• Caused by fungal organisms, particularly in immunocompromised patients.

Etiology

The infection usually develops after bacterial entry through:

• Minor skin trauma

• Surgical wounds

• Burns

• Penetrating injuries

• Insect bites

• Intravenous drug injection

• Pressure ulcers

• Perineal infections

Common causative organisms

Monomicrobial infection

• Streptococcus pyogenes

• Staphylococcus aureus (including MRSA)

Polymicrobial infection

• Streptococcus species

• Enterococcus species

• Enterobacterales

• Escherichia coli

• Klebsiella species

• Pseudomonas aeruginosa

• Bacteroides species

• Clostridium species

• Peptostreptococcus species

Pathophysiology

Necrotizing fasciitis begins when pathogenic bacteria gain access to the deep fascia through a break in the skin or by spread from a nearby infection. Once established within the fascial planes, the organisms multiply rapidly and produce powerful toxins, enzymes, and inflammatory mediators that facilitate rapid extension of infection along the relatively poorly vascularized fascia.

Bacterial exotoxins and enzymes such as streptococcal pyrogenic exotoxins, hyaluronidase, and streptokinase promote tissue destruction and impair local immune responses. Simultaneously, inflammation damages small blood vessels, causing thrombosis of the microcirculation. This vascular occlusion results in tissue ischemia, progressive necrosis, and reduced penetration of immune cells and antibiotics into infected tissues. As necrosis advances, bacteria continue to proliferate within the devitalized tissue, producing systemic release of inflammatory cytokines that may culminate in septic shock, multiorgan dysfunction, and death if urgent surgical debridement is not performed.

Risk factors

• Diabetes mellitus

• Peripheral vascular disease

• Chronic kidney disease

• Liver cirrhosis

• HIV infection

• Malignancy

• Immunosuppressive therapy

• Obesity

• Alcohol misuse

• Intravenous drug use

• Recent surgery

• Trauma

• Burns

• Pressure ulcers

• Advanced age

Clinical presentation

Necrotizing fasciitis progresses rapidly, and early recognition is essential.

Early stage

• Severe pain out of proportion to physical findings

• Fever

• Malaise

• Local swelling

• Erythema

• Warmth

• Tenderness

• Rapidly spreading cellulitis

The early clinical picture may resemble acute osteomyelitis or cellulitis.

Progressive stage

• Rapid expansion of erythema

• Skin oedema

• Bullae formation

• Foul-smelling wound discharge

• Skin anaesthesia over affected areas

• Crepitus (gas-forming infections)

• Purple or violaceous skin discoloration

Late stage

• Extensive gangrenous skin necrosis

• Large areas of black discolouration

• Tissue sloughing

• Septic shock

• Altered mental status

• Hypotension

• Tachycardia

• Multiorgan failure

• Features of streptococcal toxic shock syndrome

Diagnostic criteria

Diagnosis is primarily clinical and should never be delayed while awaiting investigation results.

Major criteria

• Rapidly progressive soft tissue infection with fascial necrosis identified during surgery

• Histopathological evidence of necrotizing fasciitis

• Positive tissue culture from deep fascia

• Intraoperative finding of grey necrotic fascia with lack of bleeding and "dishwater" fluid

Minor criteria

• Severe pain disproportionate to examination findings

• Rapid progression of erythema

• Bullae

• Skin discoloration

• Crepitus

• Fever

• Hypotension

• Elevated CRP

• Leukocytosis

• Elevated ESR

• Imaging suggestive of deep fascial infection

Investigations

Laboratory investigations

• Complete blood count (CBC)

• Erythrocyte sedimentation rate (ESR)

• C-reactive protein (CRP)

• Blood cultures before antibiotics where possible

• Serum electrolytes

• Renal function tests

• Liver function tests

• Serum lactate

• Blood glucose

• Coagulation profile

Microbiological investigations

• Deep tissue biopsy for culture and antimicrobial susceptibility testing

• Muscle biopsy for culture and sensitivity where indicated

• Aspirated pus for Gram stain and culture

Imaging

Plain X-ray

May demonstrate:

• Soft tissue swelling

• Gas within soft tissues

• Foreign bodies

Ultrasound

Useful for:

• Fascial fluid collections

• Soft tissue oedema

• Guidance for aspiration

CT scan

May demonstrate:

• Fascial thickening

• Gas tracking along fascial planes

• Fluid collections

• Deep tissue involvement

MRI

Most sensitive imaging modality where available.

Findings include:

• Fascial oedema

• Fascial enhancement

• Deep tissue necrosis

• Abscess formation

Differential diagnosis

• Cellulitis

• Erysipelas

• Pyomyositis

• Gas gangrene (clostridial myonecrosis)

• Osteomyelitis

• Deep abscess

• Compartment syndrome

• Severe diabetic foot infection

• Venous thrombosis

Management

Necrotizing fasciitis is a surgical emergency requiring immediate multidisciplinary management.

Treatment consists of:

• Immediate resuscitation

• Early broad-spectrum antimicrobial therapy

• Emergency surgical debridement

• Intensive supportive care

• Repeated surgical exploration when necessary

Pharmacological treatment

First regimen

Gentamicin

• 80 mg IV every 8 hours for 7 days

AND

Chloramphenicol

• 500 mg IV every 6 hours

With or without:

Clindamycin

• 600 mg IV every 8 hours for 7 days

Alternative regimen

Benzylpenicillin

• 2–4 million units IV every 6 hours for 7 days

AND

Clindamycin

• 600 mg IV every 8 hours

With or without:

Ciprofloxacin

• 400 mg IV every 8 hours for 7 days

Alternative regimen

Benzylpenicillin

• 2–4 million units IV every 6 hours for 7 days

AND

Clindamycin

• 600 mg IV every 8 hours for 7 days

OR

Vancomycin

• 1 g IV every 12 hours for 7 days

Antimicrobial therapy should be modified according to culture and antimicrobial susceptibility results whenever available.

Surgical management

Urgent surgery should be performed immediately once the diagnosis is suspected.

Surgical treatment includes:

• Immediate extensive surgical debridement of all necrotic tissue

• Serial debridement every 24–48 hours until no necrotic tissue remains

• Thorough wound irrigation

• Amputation when limb salvage is impossible or life-threatening infection persists

• Skin grafting or reconstructive surgery after healthy granulation tissue develops and infection has resolved

Supportive management

• Aggressive intravenous fluid resuscitation

• Haemodynamic monitoring

• Nutritional support

• Correction of electrolyte abnormalities

• Management of diabetes and other predisposing conditions

• Antipyretics for fever

• Adequate analgesia

• Physiotherapy following infection control to restore function

• Intensive care support for patients with septic shock or multiorgan dysfunction

• Blood transfusion when indicated

Monitoring and follow-up

Patients should be monitored for:

• Haemodynamic stability

• Resolution of fever

• Serial CBC, CRP, and ESR

• Renal and hepatic function during antibiotic therapy

• Wound appearance following each debridement

• Requirement for further surgical procedures

• Nutritional status

• Functional recovery during rehabilitation

Complications

• Septic shock

• Multiorgan failure

• Disseminated intravascular coagulation

• Acute kidney injury

• Extensive soft tissue loss

• Compartment syndrome

• Limb amputation

• Chronic disability

• Secondary osteomyelitis

• Death

Prevention

• Prompt treatment of skin and soft tissue infections

• Good diabetic foot care

• Early management of traumatic wounds

• Strict aseptic technique during surgery

• Appropriate wound care after trauma and surgery

• Optimisation of diabetes and immunosuppressive conditions

• Early medical assessment of rapidly progressive soft tissue infections

Patient education

Patients should be advised to:

• Seek immediate medical attention for rapidly spreading redness, severe pain, swelling, or skin discoloration.

• Complete the prescribed course of antibiotics.

• Attend all follow-up appointments and wound care visits.

• Maintain good glycaemic control if diabetic.

• Stop smoking where possible to improve wound healing.

• Maintain adequate nutrition and hydration during recovery.

• Participate in physiotherapy after wound healing to regain function.

Prognosis

Necrotizing fasciitis carries a high mortality despite modern treatment. The outcome depends largely on the speed of diagnosis, promptness of surgical debridement, adequacy of source control, causative organism, and underlying patient comorbidities. Early aggressive surgery combined with appropriate antimicrobial therapy markedly improves survival and limb salvage. Delayed treatment is associated with extensive tissue destruction, multiple surgical procedures, limb loss, prolonged hospitalization, septic shock, and increased mortality.