Key points
- Necrotizing fasciitis is a rapidly progressive infection that destroys deep soft tissues.
- Diagnosing necrotizing fasciitis can be difficult due to non-specific early symptoms.
- Primary treatment is early and aggressive surgical exploration and debridement of necrotic tissue.
- Serious complications are common and necrotizing fasciitis has a high mortality rate.
Causes
Multiple species of bacteria can cause necrotizing fasciitis. This page focuses on type II necrotizing fasciitis, which is also known as
- Hemolytic streptococcal gangrene
- Streptococcal necrotizing fasciitis
It's characterized by the isolation of Streptococcus pyogenes (group A strep bacteria) with or without other bacterial species. Staphylococcus aureus is the most common species found in co-infection cases.
Some streptococcal strains may be more likely to cause necrotizing fasciitis. Commonly involved strains, such as those containing M protein types 1, 3, 12, and 28, typically produce pyrogenic exotoxin A1.
Risk factors
Anyone, including healthy people, can get streptococcal necrotizing fasciitis. However, some factors increase a person's risk of developing it.
Certain systemic or local immunocompromising conditions increase the risk of getting necrotizing fasciitis, including:
- Cancer
- Cirrhosis
- Diabetes mellitus
- Peripheral vascular disease
Necrotizing fasciitis may also occur as a superinfection complicating varicella lesions.
Corticosteroid therapy has been shown to be a predisposing factor.
In the past, retrospective reports linked nonsteroidal anti-inflammatory drugs to necrotizing fasciitis. Prospective studies have not confirmed this linkage1.
While rare, when necrotizing fasciitis occurs it frequently happens after trauma or surgery. The trauma can be:
- Minor or unapparent trauma
- Non-penetrating trauma like bruises and muscle strain
- Penetrating trauma that breaks the skin
Clinical features
Necrotizing fasciitis can affect any part of the body, but most commonly affects extremities, particularly the legs.
Initial signs and symptoms
It usually begins with pain in the affected area accompanied by
- Erythema
- Heat
- Swelling
- Tenderness
Visually deceiving infection
The patient's pain is usually out of proportion to the signs of the local skin infection.
Treating healthcare providers may underestimate the extent of tissue infected due to:
- Spread within the subcutaneous tissue that spares the overlying skin
- Absence of lymphadenitis and lymphangitis
Superinfection secondary to varicella
Young children who develop necrotizing fasciitis as a complication of varicella may not have had obvious cutaneous signs of streptococcal infection. Three to four days after symptom onset, children may develop a high fever and appear toxic.
Quick disease progression
Within 24 to 48 hours:
- Overlying skin may turn dusky
- Cutaneous ischemia develops
- Bullae form and fill with straw-colored fluid
- Bullae progressively turn dark due to hemorrhagic fluid
Swelling progresses to brawny edema and then to dark-red induration. Skin discoloration indicates small vessels in the dermal papilla have thrombosed. Affected tissues progressively darken from red to purple to blue to black. As gangrene sets in, skin becomes anesthetized as superficial nerves die.
Signs of advanced disease
Indications of advance disease include:
- Anesthesia
- Bullae
- Crepitus
- Ecchymosis
- Necrosis
The lesions become sharply demarcated. As skin sloughs, a necrotic eschar forms, resembling a third-degree burn.
In the extremities, infection may progress to compartment syndrome, requiring emergent fasciotomy.
Diagnosis and testing
Differentiating cellulitis and necrotizing fasciitis can be difficult when presenting symptoms are non-specific:
- Edema
- Erythema
- Pain
- Unexplained fever
The following symptoms should heighten suspicion for necrotizing fasciitis2:
- Areas of decreased sensation
- Bullae
- Crepitation
- Profound pain
- Skin necrosis
Likewise, suspicion should increase for patients whose systemic findings are out of proportion to local findings.
Low suspicion
Imaging may be helpful but should never delay surgical exploration2.
Computed tomography (CT) scanning or magnetic resonance imaging (MRI) can detect subcutaneous and fascial edema or tissue gas. In the case of streptococcal necrotizing fasciitis, abscess formation or gas in the tissues are usually not seen on imaging. Muscle tear, hematoma, or prior surgery can complicate interpretation of imaging studies.
This information can be helpful early in the process when pain and swelling are present without cutaneous changes. However, these are not definitive studies.
High suspicion
Healthcare providers should expeditiously obtain:
- Prompt surgical exploration
- Gram stain
- Culture
Gram stain can be highly informative to determine whether the etiology is group A strep.
Laboratory testing
Laboratory results such as leukocytosis, thrombocytopenia, and azotemia are common.
Treatment
Primary treatment of necrotizing fasciitis is
- Early and aggressive surgical exploration
- Debridement of necrotic tissue
Surgery is coupled with appropriate broad-spectrum parenteral antibiotic therapy.
Surgery and debridement
Upon first exploration, extensive incisions that go beyond the area of apparent involvement are usually necessary. The wound should be left open and re-inspected 24 hours later to ensure adequacy of the initial debridement.
Antibiotics
Antibiotic therapy is based upon Gram stain findings. Once group A strep is confirmed to be the etiology, recommended treatment is high-dose penicillin and clindamycin (interferes with toxin production)2.
Other treatment options
Intravenous immunoglobulin may be considered in cases of severe necrotizing fasciitis, although efficacy has not been proven3.
Complications
Amputations are a common complication of necrotizing fasciitis.
As the disease progresses, patients may quickly progress to sepsis, shock, organ failure, and death.
Mortality rates
In the most recent 5 years, the mortality rate of streptococcal necrotizing fasciitis has been around 13 to 18%. It increases with age of the person affected and the presence of streptococcal toxic shock syndrome.
Prevention
Reduce the spread of group A strep bacteria with standard infection control practices, including good hand hygiene and respiratory etiquette.
Antibiotic prophylaxis
For household contacts of people with a confirmed invasive group A streptococcal infection, CDC doesn't routinely recommend:
- Antibiotic prophylaxis
- Routine screening
Special considerations
Healthcare providers may choose to offer prophylaxis to all household members of a confirmed case if the household includes someone4
- Aged 65 years or older
- At increased risk of invasive group A strep disease
- Pasternack MS, Swartz MN. Cellulitis, necrotizing fasciitis, and subcutaneous tissue infections. In Mandell GL, Bennett JE, Dolin R, editors. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. Philadelphia (PA): Churchill Livingstone Elsevier; 2015:1:1195–216.
- Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the Infectious Diseases Society of America. Clin Infect Dis. 2014;59(2):e10–52. Erratum in: Clin Infect Dis. 2015;60(9):1448. Dosage error in article text.
- Committee on Infectious Diseases. Group A streptococcal infections. In Kimberlin DW, Barnett ED, Lynfield R, Sawyer MH, editors. 32nd ed. Red Book: 2021 Report of the Committee on Infectious Diseases. Elk Grove Village (IL): American Academy of Pediatrics. 2021:633–46.
- Prevention of Invasive Group A Streptococcal Infections Workshop Participants. Prevention of invasive group A streptococcal disease among household contacts of case patients and among postpartum and postsurgical patients: Recommendations from the Centers for Disease Control and Prevention. Clin Infect Dis. 2002;35(8):950–9. Erratum in: Clin Infect Dis. 2003;36(2):243.