What are the risk factors for necrotizing fasciitis (nec fasc)?

Risk Factors for Necrotizing Fasciitis

Diabetes mellitus is the most significant risk factor for necrotizing fasciitis, present in up to 70% of cases, along with advanced age, immunosuppression, and peripheral vascular disease. 1, 2

Primary Risk Factors

Patient-Related Factors

• Diabetes mellitus (most common, present in 70.8% of cases) 2
• Advanced age (≥60 years) 3
• Multiple comorbidities (≥2 comorbidities significantly increases mortality) 3
• Immunosuppression 4
• Alcoholism 4
• Intravenous drug use 1, 4
• Peripheral vascular disease 4
• Chronic liver disease 5
• Cardiovascular disease 3

Wound/Injury-Related Factors

• Minor skin trauma (80% of cases have an initial skin lesion) 1
  • Abrasions
  • Insect bites
  • Injection sites (particularly in drug users)
  • Minor scratches
• Surgical procedures involving the bowel or penetrating abdominal trauma 1
• Chronic wounds
  • Decubitus ulcers
  • Vascular ulcers that become acutely infected 1
• Perianal or Bartholin gland abscesses 1

Clinical Warning Signs for High Mortality Risk

• Delay in surgical debridement >24 hours (most significant factor affecting mortality, with a 9.4x increased risk) 2
• Poor white blood cell response (particularly common in diabetic patients) 6
• Laboratory abnormalities:
  • High serum urea and creatinine 6, 3
  • Low hemoglobin levels 6
  • Elevated lactate >1.7 mmol/L 3
  • High LRINEC score (Laboratory Risk Indicator for Necrotizing Fasciitis) 3
• Systemic manifestations:
  • Septic shock 5
  • Disseminated intravascular coagulation 5
  • Acute renal failure 5
  • Pulmonary complications 5

Microbiological Patterns

Type 1: Polymicrobial (Most Common)

• Multiple organisms (average of 5 pathogens per wound) 1
• Often includes enteric bacteria and anaerobes 1
• Common in:
  • Perineal/scrotal infections
  • Post-surgical wounds
  • Diabetic patients

Type 2: Monomicrobial

• Group A Streptococcus (most common cause of monomicrobial necrotizing fasciitis) 2
• Staphylococcus aureus (including MRSA)
• Vibrio vulnificus
• Aeromonas hydrophila
• Anaerobic streptococci 1

Clinical Pearls and Pitfalls

• Early diagnosis is challenging - only 19% of cases are correctly diagnosed upon admission, with 48.6% initially misdiagnosed as cellulitis 6
• Paucity of specific skin findings early in the disease course makes diagnosis difficult 2
• Prior antibiotic treatment can mask the severity of infection and modify clinical presentation 2
• Wooden-hard feel of subcutaneous tissues is a distinguishing clinical feature 1
• Disproportionate pain relative to physical examination findings should raise suspicion 7
• Failure to respond to initial antibiotic therapy suggests deeper tissue involvement 1
• Systemic toxicity with altered mental status is a concerning sign 1

Remember that necrotizing fasciitis requires immediate surgical debridement, as delay in surgical intervention is the most significant factor associated with increased mortality 2, 5.