The incidence has been reported approximately 1,000 cases per year in the United States or 0.4 to 0.53 cases per 100,00045. Not only individuals with pre-existing co-morbidities are affected but also young and healthy individuals can be affected. NSTI can be classified according to the anatomic location involved or the depth of infection as necrotizing adiposities, fasciitis, or myositis. Most commonly NSTI is classified on the basis of microbiology as type I, being polymicrobial, type II, being monomicrobial and type III, being caused by marine vibrio species. These classification systems are not clinically significant as they do not change the management of the patient. This condition can involve any part of body but primarily involves extremities, abdomen or perineum. Anaya et al in their study of 150 established cases of necrotizing fasciitis estimated that extremities were the most common site of infection in 57.8% followed by the abdomen and perineum 6.

There are two main groups of necrotizing fasciitis depending on microbiology. Type-I NF are polymicrobial. Approximately 55% to 75% of all cases result from type I infection and most common bacterial species include Gram-positive cocci (streptococci, staphylococcal species), enterococci and gram-negative enterobacteriaceae (Escherichia coli, Acinetobecter species, Pseudomonas species and Klebsiella species). Bacteroides species are the most common anaerobes, while Clostridial species are an infrequent isolate 7891011. Type I infections are often diagnosed in immunocompromised patients and tend to occur in the perineal and trunk areas 12. Type-II infections are monomicrobial and usually caused by group A Streptococcus (Streptococcus pyogenes) either alone or in association with Staphylococcus aureus. Streptococal infection can be associated with toxic shock syndrome. Recently there has been an increasing incidence of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) soft-tissue infection, particularly in IV drug abusers 131415. Some other organisms has been reported as a rare cause of type-II infection like Klebsiella species 16 and group-B streptococcus 17. Type II NF is far less common than type I infection and tends to occur in otherwise healthy, young, immunocompetent hosts and is classically located on the extremities. There is another subtype due to marine Vibrio species (e.g. V. vulnificus) 18 associated with marine injuries and contact with raw sea food. Although this is the least common type, it is associated with a fulminant course and can lead to multisystem organ failure within 24 hours of infection. Wong et al 10 in their study of 89 patients with necrotizing fasciitis described the causative micro organisms as obtained from first debridement sample. According to their study a single organism was identified in twenty-five patients (28.1%), multiple organisms were identified in forty-eight patients (53.9%), and no organism was identified in sixteen patients (18.0%). Streptococcal species, identified in thirty-one patients, were the most common isolates. Forty-eight (66%) of the positive cultures were polymicrobial necrotizing infections (Type-I NF).

Necrotizing fasciitis is characterized by rapidly spreading infection in the subcutaneous tissues. Microbial invasion of the subcutaneous (SC) tissues occurs either through external trauma or direct spread from a perforated viscus (particularly colon, rectum, or anus). Bacteria then track SC, producing endo and exotoxins 19 that cause micro-vascular thrombosis20, tissue ischemia, liquefactive necrosis, and often systemic illness 21 which can progress to septic shock, multisystem organ dysfunction, and death. Tissue ischemia, impedes oxidative destruction of bacteria by polymorphonuclear cells and prevents adequate delivery of antibiotics. Hence, surgical debridement is the mainstay therapy for NSTI, and antibiotic therapy alone is of little value and only mask the severity of the symptoms 22.

The commonest predisposing factor for NF of extremity is a history of drug abuse and multiple needle punctures in the affected site, this was found in 129 (33%) patients in a systematic review of NF of upper and lower limb23. Other predisposing factors include trauma, fish-fin injury, chronic skin ulcer, burns, post operative wound infection, insect bite and colo-cutaneous fistula 24252627.

Diabetes Mellitus(DM) is the leading predisposing underlying medical condition because of peripheral neuropathy, peripheral vascular disease and immuno-suppression. According to Elliot et al 7 presence of DM does not affect mortality unless it occur with certain other diseases. Other associated diseases include immuno-deficiency, alcoholism, chronic renal failure, liver cirrhosis, HIV, malignancy, steroids and peripheral vascular disease 282930.

Lack of cutaneous findings early in the disease make the diagnosis challenging and high index of suspicion is essential. Common sign and symptoms of the disease are summarized in [Table 1]. The most common early signs are erythema, local warmth, skin induration, and edema. These signs often make early diagnosis difficult and the condition is often diagnosed as cellulites, abscess or septic arthritis as in our case and the diagnosis of necrotizing fasciitis is only suspected when patient fail to respond to broad spectrum intravenous antibiotics or develop cutaneous manifestations. Pain out of proportion to the apparent severity of the lesion should alert the physician to the possible diagnosis of Necrotizing fasciitis. Patches of skin necrosis, tissue crepitus, fluctuance and systemic evidence of sepsis such as hyperthermia, tachycardia and hypotension are alarming signs.

Early diagnosis of NF is not always possible due to paucity of cutaneous findings early in the disease therefore high index of suspicion is important in infected cases that are refractory to antibiotics. There are a wide variety of diagnostic tools that can be used as an adjunct for diagnosis.

Wong et al. 31 created a score (laboratory risk indicator for necrotizing fasciitis score) to discriminate between NSTI and non-necrotizing soft-tissue infection. They identified 6 independent variables associated with NSTI. Each variable, if present, gives a specific number of points toward the final score [Table 2]. The total score had a range of 0–13, and Wong and colleagues showed that, for intermediate and high-risk patients (score, > 6) had a PPV of 92% and a NPV of 96% 31.

Other diagnostic adjuncts like ultrasound, CT scan and magnetic resonance imaging (MRI) are helpful in suspicious cases. The usefulness of MRI in the diagnosis of NF has been supported in a study by Rahmouni et al. 32, who in 36 patients were able to differentiate between non-necrotizing cellulites that would respond to medical treatment and severe necrotizing infection that require rapid, life-saving surgery. Wang and Hung 33 investigated the use of tissue oxygen monitoring with near-infrared spectroscopy for the diagnosis of NF. They reported that tissue oxygen saturation less than 70% had a sensitivity of 100% and a specificity of 97%. The authors of this study propose that this method may offer a reliable non-invasive approach of assessing lower extremities at risk of necrotising fasciitis. Examination of a frozen section biopsy specimen from the compromised site that includes deep fascia and possibly muscle has been suggested as well, as a means to achieve earlier diagnosis of NSTI in patients 2034.

Early diagnosis and prompt treatment including surgical debridement and braod spectrum antibiotics is the key to successful treatment in necrotizing fasciitis 3536. The initial regimen should include agents effective against aerobic gram-positive cocci, gram-negative rods, and a variety of anaerobes 37. The usual multidrug regimens include high-dose penicillin, high-dose clindamycin, and a fluoroquinolone or an aminoglycoside for coverage of gram-negative organisms. Vancomycin, or linezolid should be considered until MRSA infection has been excluded 3. This should be accompanied with supportive measures such as fluid replacement, blood pressure support, analgesia, nutritional support and intensive care involvement etc. Intravenous immunoglobulins (IVIg) 3839 and Hyberbaric oxygen (HBO) therapy has also been suggested as an adjunct to other treatments. There is no agreement as to the usefulness of HBO for NF 4041.

When NF is established or highly suspected, urgent exploration and debridement of tissue is the cornerstone of successful management 37. Surgical exploration also aid in the diagnosis of NF. The operative findings of grayish necrotic deep fascia, a lack of resistance to blunt dissection, lack of bleeding of the fascia, and presence of foul-smelling "dishwater" pus confirms the diagnosis. Tissue samples should be sent for gram staining, culture and histology. C H Wong 42, described his approach to debridement in NF which consists of 4 steps: (1) confirming the diagnosis (2) defining the extent of fasciitis; (3) surgical excision; and (4) post-excision wound care. The extent of the infection is defined by probing the wound bluntly, followed by systematic excision. He classified the infected skin into zones 1, 2, and 3. Zone 1 is necrotic tissue. Zone 2 is infected but potentially salvageable soft tissue, and zone 3 is non-infected skin. Zone 1 is completely excised. Zone 2 is meticulously assessed and cut back as necessary to remove nonviable tissue while maximally preserving salvageable tissue. Zone 3 is left alone.

The aim of surgical debridement is to remove all infected tissue in a single operation. This halts the progression of the fasciitis and minimizes unnecessary returns to the operating room. In most of the cases repeat debridement in needed before wound closure.

Wound closure should be carefully planned as early closure carries the risk of residual infection and poor wound healing. The wound must demonstrate that the healing phase has started before any attempt to closure. Several methods has been used for wound closure such as secondary suturing, shoe lace technique, skin grafting, muscle flaps etc. Vacuum-assisted closure (VAC) 24 technique has found an extended use in the field of open wound management and has shown decreased morbidity associated with wound care.

The mortality associated with the disease is high and has been reported from 6% to as high as 76% 434445464748495051 [Table 3]. McHenry et al 9 in their study reviewed the determinants of mortality in patients with necrotizing soft tissue infections. They summarized the reported mortality rates from different studies. The cumulative mortality rate was 34% (6% to 76%) and 29% in their series of patients. The average time from admission to operation was 90 hours in non-survivors versus 25 hours in survivors. They concluded that early debridement was associated with a significant decrease in mortality. Similar findings were also reported by Wong et al 10. In a retrospective review of 89 consecutive patients with necrotizing fasciitis, they concluded that the most common associated co-morbidity was diabetes mellitus (sixty-three patients; 70.8%). Advanced age, two or more associated co-morbidities, and a delay in surgery of more than twenty-four hours adversely affected the outcome. Multivariate analysis showed that only a delay in surgery of more than twenty-four hours was correlated with increased mortality 10.