All of the following statements about Necrotizing fascitis are true, except
Necrotizing fasciitis

Necrotizing fasciitis is a rare but life-threatening rapidly progressive bacterial infection of subcutaneous tissue and superficial fascia that is potentially fatal if appropriate treatment measures are not instituted quickly.
Usually occurring after compromised skin integrity because of infection or trauma, necrotizing fasciitis is manifested by flagrant inflammatory features at the site of infection that may be accompanied by hemorrhagic bullae, necrosis, and crepitus, often unresponsive to antibiotic therapy Systemic septic features may arise.

Most common site

Necrotizing fasciitis frequently affects the lower limbs, although any site may be involved, including the head and neck. Necrotizing fasciitis of the perineum is known as Fournier's Gangrene.

Etiological agents

Necrotizing fasciitis can be a polymicrobial infection with a mixture of Gram-positive and Gram-negative aerobes and anaerobes (Type I) or it can be monomicrobial (Type II) with group A streptococcus being the most common isolate.

Predisposing, factors

Predisposing factors include trauma (often trivial), burns, splinters, surgery, childbirth, diabetes mellitus, varicella, immunosuppression, renal failure, arteriosclerosis. odontogenic infection, malignancy, and alcoholism. Nonsteroidal and inflammatory agents may alter the immune response, causing a minor infection to become fulminant.

Clinical manifestation

Extension from a skin lesion occurs in 80% of cases. The initial lesion is often trivial, such as a minor abrasion, insect bite, injection site (drug addicts) or boil; 20% of patients have no visible skin lesion.
Initially, there is a pain, erythema, edema, cellulitis, and high fever.
The patient may be disoriented and lethargic. The local site shows cellulitis (90% of cases), edema (80%), skin discolouration or gangrene (70%), and anaesthesia of involved skin.
A wooden-hard feel of the subcutaneous tissues is characteristic.
The most consistent clinical clue is unrelenting pain out of proportion to the physical findings even if there is only mild or no fever or erythema. Typically there is diffuse swelling of an arm or leg and intense pain on palpation. About 1 or 2 days after symptom onset, the patient has a high fever, leukocytosis, edema with central patches of dusky blue discolouration, weeping blisters, and borders with cellulitis. Bullae with clear fluid rapidly turn violaceous.
Septicemia may develop secondarily and should be strongly suspected in the presence of fever, anorexia, nausea, diarrhea, confusion, and hypotension. Progression to gangrene, sometimes with myonecrosis, and an extension of the inflammatory process along fascial planes are possible.
Twenty-five percent will die of septic shock and organ failure 

Treatment

Early supportive care, surgical debridement, and parenteral antibiotic administration are mandatory.
All devitalized tissue should be removed to freely bleeding edges, and repeat exploration is generally indicated within 24-36 hr to confirm that no necrotic tissue remains. The mortality rate is nearly 100% without surgical debridement.
Infection of fascia and subcutaneous tissue
Most commonly caused by Group A beta hemolytic streptococci
Most common site is perineum followed by trunk and extremities
Surgical debridement is mandatory