Author: Vanessa Ngan, Staff Writer, 2003. Updated by Dr Jannet Gomez, Postgraduate Student in Clinical Dermatology, Queen Mary University London, United Kingdom; Chief Editor: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand, February 2016.
Necrotising fasciitis is a very serious bacterial infection of the soft tissue and fascia (a sheath of tissue covering the muscle). The bacteria multiply and release toxins and enzymes that result in thrombosis (clotting) in the blood vessels. The result is destruction of the soft tissues and fascia.
The main types of necrotising fasciitis are:
Bacteria causing type 1 necrotising fasciitis include Staphylococcus aureus, Haemophilus, Vibrio and several other aerobic and anaerobic strains (Escherichia coli, Bacteroides fragillis). It is usually seen in the elderly or in patients affected with diabetes or other conditions.
Type II necrotising fasciitis has been sensationalised in the media and is commonly referred to as flesh-eating disease. It affects all age groups. Healthy people are also prone to infection with this group.
Type III necrotising fasciitis is caused by Clostridia perfringens or less commonly Clostridia septicum. It usually follows significant injury or surgery and results in gas under the skin: this makes a crackling sound called crepitus. IV drug users injecting “black tar” heroin subcutaneously can also be infected with clostridia and develop necrotising fasciitis.
Necrotising fasciitis due to marine organisms is usually due to contamination of wounds by sea water, cuts by fish fins or stingers, or consumption of raw seafood. It occurs more commonly in patients with liver disorders. These infections can be very serious and can be fatal if not attended within 48 hours.
Fungal necrotising fasciitis complicates traumatic wounds in immunocompromised people.
Other terms used for necrotising fasciitis include haemolytic streptococcal gangrene, Meleney ulcer, acute dermal gangrene, hospital gangrene, suppurative fasciitis, and synergistic necrotising cellulitis.
Necrotising fasciitis affecting perineal, genital and perianal regions is known as Fournier gangrene. This has a particularly high death rate ranging from 15% to 50%.
Necrotising fasciitis may occur in anyone, in fact, almost half of all known cases of streptococcal necrotising fasciitis have occurred in young and previously healthy individuals. The disease may occur if the right set of conditions is present, these include:
Risks for necrotising fasciitis include:
Infection starts in the superficial fascia. Enzymes and proteins released by the responsible organisms cause necrosis of fascial layers. Horizontal spread of infection may not be clinically apparent on the skin surface and hence diagnosis may be delayed. Infection then spreads vertically up into the skin and down into deeper structures. Thrombosis occludes the arteries and veins leading to ischaemia and necrosis of the tissues.
Aerobic and anaerobic bacteria produce hydrogen, nitrogen, hydrogen sulfide, and methane gases that destroy hyaluronic acid enabling spread of infection.
Signs and symptoms vary between individuals but often some or all of the following are present.
As necrotising fasciitis takes hold:
By about days 4–5, the patient is very ill with dangerously low blood pressure and high temperature. The infection has spread into the bloodstream and the body goes into toxic shock. The patient may have altered levels of consciousness or become totally unconscious.
Metastatic abscesses can develop in liver, lung, spleen, brain, pericardium, and rarely, in the skin.
A thorough history and clinical examination are crucial in arriving at the diagnosis of necrotising fasciitis. Special care should be taken when examining immunocompromised patients, as presentation of symptoms/signs may be atypical.
These usually show:
Blood culture, deep tissue biopsy and Gram stain help in identifying the culprit organism(s) and guide the choice of antibiotic. If Staphylococcus aureus is detected, MRSA sensitivity test should be done. Blood cultures are usually negative for clostridial species.
Fungal culture should be performed in immunocompromised and trauma patients.
X-ray, CT and MRI identify areas of fluid collection, inflammation and gas within the soft tissues.
The Laboratory Risk Indicator for Necrotising Fasciitis (LRINEC) is a tool that aids in distinguishing necrotising fasciitis from other tissue infections based on six parameters. A score of ≥ 6 favours necrotising fasciitis. This test is not appropriate for all cases and is not completely reliable.
CRP (mg/L) ≥150:
WBC count (×103/mm3):
Sodium (mmol/L) <135:
Creatinine (umol/L) >141:
Glucose (mmol/L) >10:
Once the diagnosis of necrotising fasciitis is confirmed, treatment should be initiated without delay.
Immediate surgical debridement improves survival and avoids comlications of necrotising fasciitis. All the infected tissue should be cleared away using adequate excision. Repeated debridements are carried out for a few days.
When the acute infection has subsided, the wound should be closed with skin grafting if required. Vacuum-assisted wound closing devices may be useful to heal a persistent ulcer.
Prompt diagnosis and treatment is essential to reducing the risk of death and disfigurement from necrotising fasciitis.
If diagnosed and treated early, most patients will survive necrotising fasciitis with minimal scarring. If there is significant tissue loss, later skin grafting will be necessary and in some patients amputation of limbs is required to prevent death.
Up to 25% of patients will die from necrotising fasciitis, due to complications such as renal failure and septicaemia (blood poisoning) and multiorgan failure.
See the DermNet NZ bookstore
© 2018 DermNet New Zealand Trust.
DermNet NZ does not provide an online consultation service. If you have any concerns with your skin or its treatment, see a dermatologist for advice.