Medical Illustrations

Necrotizing fasciitis is a dangerous infection of soft-tissue that starts in the subcutaneous tissue (just below the skin) and spreads along the flat layers of fibrous tissue that separate different layers of tissue (fascial planes). It most commonly occurs in the arms, legs and abdominal wall. The death rate is up to 40%.

Necrotizing fasciitis can be caused by only one type of bacteria (monomicrobial) or by a combination of bacteria such as E. coli and Bacteroides fragilis or clostridium (polymicrobial). Monomicrobial infections account for 10% and polymicrobial for 90% of cases of necrotizing fasciitis.

Symptoms include redness (erythema), swelling (edema) and tenderness. The degree of pain typically is greater than the severity of these findings and the person appears terribly ill. The original skin wound is often evident. Skin changes may include bullous lesions (blisters) and local skin anesthesia (due to blocking of little vessels in the skin). A crinkly or crackling feeling called crepitus indicates gas in the tissues but occurs in only about half of cases.

Emergency diagnosis and treatment are essential. Broad-spectrum antibiotic treatment and prompt surgical removal of dead and infected tissue decreases the death rate.