Necrotizing fasciitis (also known as flesh-eating disease) is a rapidly progressive bacterial inflammatory infection that affects fascia and causes necrosis (the death) of the soft subcutaneous tissues of the body. Necrotizing fasciitis affects occurs with a rate of 0.4 in every 100,000 people per year in the USA.
Necrotizing fasciitis is a severe condition that progresses very quickly and spreads along fascia planes. The same condition affecting the genitals and perineal area is called Fournier gangrene. The mean age of the patient with necrotizing fasciitis is around 40. The disease rarely affects children. Most of the patients are male. The main complications of necrotizing fasciitis include renal failure, septicemia, limb loss and death. Around 25% of affected people die.
The disease is caused by the variety of bacterial agents: aerobic, anaerobic or mixed flora. The 3 different types of the process are distinguished in dependence on the bacteria that cause the fasciitis:
- Type I, or polymicrobial
- Type II, or group A streptococcal
- Type III gangrene, or clostridial myonecrosis
- Type IV fungal infection (extremely rare)
Up to 80% of cases of necrotizing fasciitis are caused by several bacteria. Methicillin-resistant Staphylococcus aureus (MRSA) is involved in up to a third of cases.
Infection begins locally at a site of trauma or injury even minor. In some cases necrotizing fasciitis appears to be the complication of the surgeries or invasive procedures. The bacteria destroy the soft tissues under the skin including muscles by releasing the bacterial toxins (exotoxins).
The bacteria usually is killed by body’s immune system, that’s why the condition is uncommon among the healthy persons. Those whose immunity is weaken or the ones who suffer from the immunodeficiency, cancer, diabetes or get immunosuppressive treatment are at risk of developing necrotizing fasciitis. The immune system is weaken also in people who overuse alcohol, have obesity, chronic systemic disease or use drugs intravenously.
The main complain is the intense local pain. Commonly the necrotizing fasciitis involves limbs and genitals. People have initially inflammation, fever and tachycardia (fast heart rate). Within hours the area swells, becomes hot, the skin changes color from red (erythema) up to violet and blisters appear. The accumulation of fluids and gases (in case of anaerobic bacteria) produces crepitus while doctor touch the affected part. The affected area tends to extend rapidly causing gangrene. Fascial necrosis is typically more advanced than it can be suggested by the appearance. Sometimes skin appears to be insensitive (anaesthesia) due to the necrosis and death of the nerve fibers.
Fournier gangrene in males begins with local tenderness, itching, edema, and erythema. This leads to necrosis of the scrotal fascia. The scrotum enlarges progressively.
The bacteria toxins along with the products of muscles deterioration leaks into the blood flow and leads to shock progression and multiple organ failure. If not treated the disease leads to sepsis and subsequent death.
The visual appearance of the affected area is very characteristic. Although several another tests are required to confirm the diagnosis such as blood and urine tests, bacteriological examination to identify the type of bacteria that caused the fasciitis, blood cultures, biopsy, X-ray, CT or MRI.
To determine the necrotizing fasciitis The Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score can be used. A score includes levels of 6 serologic measures: C-reactive protein, total white blood cell count, hemoglobin, sodium, creatinine and glucose.
The treatment should begin as soon as the diagnosis is known. Intravenous antibiotics should be administered immediately after the cultures are taken. Penicillin G and an aminoglycoside (if renal function permits), as well as clindamycin (to cover streptococci, staphylococci, gram-negative bacilli, and anaerobes) may be used.
The condition is believed to be a surgical emergency case that’s why the aggressive surgical removal of infected tissues is the only possible effective treatment. Early surgical treatment may minimize tissue loss, and helps avoid the amputation of the infected limb. Sometimes the repeated explorations of the affected area are needed. It is important to eliminate the all necrotized tissues. Almost all of the patients need skin grafting after the recovery.
The disease involves the whole body, so that patients require monitoring of the main vital functions in an intensive care unit. They need intravenous injections of fluids and nutrition. A streptococcal shock syndrome can be treated effectively with the intravenous immunoglobulin.
Some reported that hyperbaric oxygen therapy can reduce mortality rates.