This is an uncommon soft tissue infection that spreads along fascial planes with relative initial sparing of skin and underlying muscle. As the infection progresses, necrosis of the overlying skin occurs as a result of thrombosis of cutaneous vessels.
Bacteriologically, two types of infection are described. Type I infection is caused by a combination of at least one anaerobe and one or more facultative anaerobes such as streptococci or enterobacteriaceae. Type II infection is caused by group A P-hemolytic streptococci alone or in combination with staphylococci (38). Recently, Howard et al. have described necrotizing fasciitis on exposure of nonintact skin to salt-water-borne halophilic marine vibrios (39). Tissue damage and systemic toxicity are as a result of release of endogenous cytokines and bacterial toxins.
The most common sites for infection include the abdominal wall, perineum, and extremities. Visceral metastatic abscesses may form in various viscera. The source of introduction of the pathogen may be unknown or may follow surgery (40), minor trauma, or hematogenous spread from a distant site. Most cases involving the vulva occur in obese diabetic patients and often begin as Bartholin's gland duct abscess or a vulvar abscess (41,42).
Severe local pain with relative paucity of local signs of inflammation characterize early disease (43). Fever and systemic toxicity may be marked. An erythematous, swollen, tender, hot area of cellulitis spreads along unseen fascial planes to involve contiguous areas away from the original site of involvement.
Thrombosis leads to serous and subsequently hemorrhagic bullae, gangrene, ulceration, and "dishwater pus" because of liquefactive necrosis. Lymphadenitis and lymphangitis are rare. Crepitance is palpable in approximately half of the cases. Destruction of subcutaneous nerves leads to anesthesia.
Early diagnosis is aided by a high index of suspicion and the ability to pass a probe unimpeded along normally adherent fascial planes (44). The necrotic center of the lesion is preferred for obtaining both aerobic and anaerobic cultures and Gram's stain in contrast to the leading edge of the lesion in cellulitis. Plain radiographs, ultrasonography, CT scan, and MRI may aid the diagnosis by detecting soft tissue gas and define extent of disease.
Surgical intervention forms the cornerstone of therapy. Early and adequate surgical debridement and fasciotomy play a key role in reducing mortality. Antibiotics are very important adjunctive therapy. The choice of antibiotics include penicillin or cephalosporins in combination with an aminoglycoside and anaerobic coverage with either clindamycin or metronidazole. Following initial empiric therapy, continued antibiotic therapy can be tailored according to culture and susceptibility results.
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