The diagnosis is often difficult to make early in the disease course. Most patients with necrotizing fasciitis develop erythema, edema, and pain, which in the early stages of the disease is disproportionately greater than that expected from the degree of cellulitis present and characteristically extends beyond the border of erythema (105). Late in the course of the infection, the involved skin may be anesthetized secondary to necrosis of superficial nerves. Temperature abnormalities, both hyperthermia and hypothermia, are concomitant with the release of bacterial toxins and with bacterial sepsis (104). The involved skin is initially tender, erythematous, and warm. Edema develops, and the erythema spreads diffusely, fading into normal skin, characteristically without distinct margins or induration. Subcutaneous microvascular thrombosis induces ischemia in the skin, which becomes cyanotic and blistered. As necrosis develops, the skin becomes gangrenous and may slough spontaneously (104). Most patients will have leukocytosis and acid-base abnormalities. Subcutaneous gas may develop, which can be identified by palpation and by radiography. The finding of subcutaneous gas by radiography is often indicative of clostridial infection, although it is not a specific finding and may be caused by other organisms. These organisms include Enterobacter, Pseudomonas, anaerobic streptococci, and Bacteroides, which, unlike clostridial infections, spare the muscles underlying the affected area. A tissue biopsy specimen for Gram stain and aerobic and anaerobic culture should be obtained from the necrotic center of the lesion to identify the etiologic organisms (105). Although necrotizing fasciitis often is diagnosed during surgery, a high index of suspicion and liberal use of frozen-section biopsy can provide an early life-saving diagnosis and minimize morbidity (104).
Predisposing risk factors for necrotizing fasciitis include diabetes mellitus, alcoholism, an immunocompromised state, hypertension, peripheral vascular disease, intravenous drug abuse, and obesity (104). The most frequent site of infection is in the extremities, but the infection can occur anywhere in the subcutaneous tissues, including the head and neck, trunk, and perineum. Necrotizing fasciitis occurs after trauma, surgery, burns, and lacerations; as a secondary complication in perirectal infections or Bartholin duct abscesses; and de novo (103,106– 109). Increased age, delay in diagnosis, inadequate debridement during initial surgery, extensive disease at the time of diagnosis, and the presence of diabetes mellitus are all factors that are associated with an increased likelihood of mortality from necrotizing fasciitis (104–106). Early diagnosis and aggressive management of this lethal disease contribute to improved survival.