This uncommon, severe infection involves the subcutaneous soft tissues, including the superficial and deep fascial layers, with early skin sparing and late muscle involvement. It is most commonly seen in the lower extremities, abdominal wall, and perianal and groin area, as well as in postoperative wounds. It is commonly spread from a trauma site, surgical wound, abscess, or decubitus ulcer. Alcoholism, parenteral drug abuse, and diabetes are predisposing factors. Pain, tenderness, erythema, swelling, warmth, shiny skin, lymphangitis, and lymphadenitis are early findings. Later, there is rapid progression of bullae with clear pink or purple fluid and cutaneous necrosis. The skin becomes anesthetic, and subcutaneous gas may be present. Systemic toxicity may be manifest by fever, dehydration, leukocytosis, and frequently positive blood cultures. Type I includes anaerobic species (Bacteroides and Peptostreptococcus) and type II includes either group A streptococci alone or group A streptococci with S aureus.
Prompt diagnosis is critical; if made within 4 days from symptom onset, the mortality rate is reduced from ~50% to 12%. Initial treatment involves resuscitation with volume expansion, operative debridement, and prompt initiation of broad-spectrum antibiotics.