Diagnosis: Necrotizing fasciitis
Necrotizing fasciitis infections are characterized by fulminant destruction of tissue, systemic signs of toxicity, and high rates of mortality. The incidence of necrotizing fasciitis in adults is 0.40 cases per 100,000 population, while the incidence in children is 0.08 cases per 100,000 population. Mortality rates as high as 73% have been reported.1 Early clinical suspicion, early surgical intervention (surgical debridement), and systemic antibiotics are of the utmost importance.
Necrotizing fasciitis is caused by gram positive, gram negative, and/or anaerobic bacteria. Local tissue hypoxia from trauma, surgery, or a medically compromised state creates an ideal opportunistic environment for bacterial proliferation.
Necrotizing fasciitis can be broadly classified into 2 main types:
Type 1 necrotizing fasciitis is a polymicrobial infection caused by facultative bacteria along with anaerobes. Polymicrobial infections with anaerobes are common (up to 74%) in infected puncture wounds in patients with diabetes.2
Type 2 necrotizing fasciitis is caused by group A streptococci alone, but sometimes in association with Staphylococcus aureus. Vibrio vulnificus infection has also been reported in fish bone piercing injuries leading to necrotizing fasciitis.3
Typical early signs and symptoms include severe pain, rapidly progressing erythema, dusky or purplish skin discoloration, and systemic signs of septic toxicity such as fever, tachycardia, a generalized unwell feeling, and even hypotension. (A lack of classic tissue inflammatory signs may mask an ongoing necrotizing fasciitis beneath the skin.) The involved region may become numb due to the necrosis of the innervating nerve fibers. Discharge or crepitus may also be noted.
Late clinical signs of necrotizing fasciitis include cellulitis, skin discoloration, discharge of “dishwater” fluid, blistering, and hemorrhagic bullae. Findings of crepitus and soft tissue air on plain radiographs are seen in 37% and 57% of patients, respectively.4 Our patient’s X-ray findings revealed extensive gas pockets within soft tissue and osteomyelitis changes of the 5th metatarsal head.
The differential diagnosis for necrotizing fasciitis includes:
- pyogenic soft tissue cellulitis
- clostridial cellulitis (which may also present with soft tissue crepitus)
- nonclostridial anaerobic cellulitis
- acute febrile neutrophilic dermatosis
- acute hemorrhagic edema of infancy
- erythema induratum (nodular vasculitis).