What is necrotising fasciitis?
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.
There are three main types of necrotising fasciitis:
- Type I (polymicrobial i.e. more than one bacteria involved)
- Type II (due to haemolytic group A streptococcus)
- Type III (gas gangrene)
Bacteria causing type 1 necrotising fasciitis include Staphylococcus aureus, Haemophilus, Vibrio and several other aerobic and anaerobic strains. It usually follows significant injury or surgery.
Type II necrotising fasciitis has recently been sensationalised in the media and is commonly referred to as
Type III 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.
How do you get necrotising fasciitis?
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:
- An opening in the skin that allows bacteria to enter the body. This may be very minor such as a small cut, graze or pinprick or a large wound due to trauma or surgery. Sometimes no point of entry can be found.
- Direct contact with a person who is carrying the bacteria or the bacteria is already present elsewhere on the person.
- Particularly invasive strains of streptococci or other bacteria
- In children, type II necrotising fasciitis may complicate chickenpox
- The risk is increased in those taking aspirin or non-steroidal anti-inflammatory drugs.
Those at increased risk of necrotising fasciitis include diabetics, immunosuppressed individuals, obese people, drug abusers, and people with severe chronic illness.
What are the signs and symptoms of necrotising fasciitis?
Signs and symptoms vary between individuals but often some or all of the following are present.
- Symptoms appearing usually within 24 hours of a minor injury:
- Pain in the general area of the injury and worsening over time
- Flu-like symptoms such as nausea, fever, diarrhoea, dizziness and general malaise
- Intense thirst as body becomes dehydrated
Within 3-4 days of the initial symptoms the following may occur:
- Affected area starts to swell and may show a purplish rash
- Large dark marks form that turn into blisters filled with dark fluid
- Wound starts to die and area becomes blackened (necrosis)
- Severe pain
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.
What treatment is available?
Once the diagnosis of necrotising fasciitis is confirmed, treatment should be initiated without delay. Patients must be hospitalised, the causative organism(s) identified and treated with high dose intravenous antibiotics, often in an intensive care unit.
It is absolutely vital than an experienced surgeon urgently removes all dead tissue.
Treatment to raise blood pressure, hyperbaric oxygen, and intravenous immunoglobulin may also be necessary.
What is the likely outcome?
If diagnosed and treated early, most patients will survive with minimal scarring. However 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 the disease and complications such as renal failure and septicaemia (blood poisoning) increase the likelihood of death.
Prompt diagnosis and treatment is essential to reducing the risk of death and disfigurement from necrotising fasciitis.
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On DermNet NZ:
- Necrotising fasciitis – pathology
- Streptococcal skin infections
- Bacterial infections online course for health professionals
- Dermatologic Manifestations of Necrotizing Fasciitis – Medscape Reference