Recent media attention has been drawn to necrotizing fasciitis, often described as an infection caused by “flesh-eating bacteria”.  Media outlets have recently reported severe illness and deaths associated with this infection.  Necrotizing fasciitis is a severe, life threatening infection of the subcutaneous tissues and fascia, which may be caused by several different micro-organisms. The mortality is as high as 40%. The infection can lead to shock, loss of limb, and death, necessitating prompt recognition and treatment.

Necrotizing fasciitis is most often caused by Group A Streptococcus.  Some types associated with gas formation may be caused by C. perfringens. Less commonly, it may also be caused by MRSA, mixed aerobic–anaerobic bacteria, E. coli, Bacteroides, or S. pyogenes.

Patients typically present with a history of a break in the skin, though they may report a history of an injury that did not break the skin, such as a bruise.  Patients typically present with fever and severe pain/erythema in the area of infection.  A hallmark finding of necrotizing fasciitis is pain out of proportion to exam. In later stages, the infected area appears more red/purple with worsening edema, associated bullae and skin sloughing.  As the infection progresses, frank necrosis develops. 

Some patients are at higher risk for development of necrotizing fasciitis.  These patients include those with diabetes, vascular disease, renal disease, and those that are immunosuppressed.  Individuals with recent IV drug use, recent surgeries, or recent penetrating injuries are also at an increased risk.

Rapid recognition is vital for ensuring positive patient outcomes.  Cellulitis is the most common misdiagnosis.  However, unlike cellulitis, patients with necrotizing fasciitis decompensate quickly.  They have pain out of proportion to exam and quickly progress to development of shock.  A high degree of clinical suspicion must be maintained in order to diagnose this condition before development of shock.  Patients should receive a complete blood count, basic metabolic panel, and blood cultures.  Broad spectrum antibiotics are the standard of care.  Surgical consultation is also considered standard of care.  Surgical debridement is typically required for treatment, with amputation required in extreme cases. 

Read more:

Critical Care: Chapter 47: Skin Complications

Harrison's Principles of Internal Medicine, 20e: Chapter 124: Infections of the Skin, Muscles, and Soft Tissues