Idiopathic necrotizing fasciitis: risk factors and strategies for management.

The prognosis of necrotizing fasciitis (NF) depends on early diagnosis and management. Idiopathic NF may be more challenging, because it occurs in the absence of a known causative factor. Therefore, our purpose in this study was to identify the distinct features of idiopathic NF that may be important in early recognition of this disease and determine the factors associated with mortality. A retrospective chart review was performed in patients with a diagnosis of NF between 1988 and 2003. Patients were classified as idiopathic and secondary NF, and data were analyzed in terms of etiological and predisposing factors, causative microbiological organisms, and clinical outcome. The study included 98 patients, 63 men and 35 women, with a diagnosis of NF. The median age was 55.5 years (range, 13 - 80). Idiopathic NF occurred in 60 of 98 patients (61%). The principal anatomic sites of infection for NF were perineal localisation in 55 patients (66%) and extremities in 31 patients (32%). Characteristics that distinguish patients with idiopathic NF from secondary NF were as follows: age older than 55 years (P = 0.0001), presence of comorbid illnesses like DM (P = 0.007) or chronic renal failure (P = 0.041), and perineal localization (P = 0.008). By logistic regression analysis, independent risk factors for idiopathic NF remained age > 55 years and perineal localization as statistically significant factors, when all the significant variables found in univariate analysis were included in the model. The majority of patients (82%) had polymicrobial infections. The mortality rate was 35 per cent. All patients were treated with radical surgical debridement and a combination of antibiotics. Female gender, presence of malignant disease, and diabetes mellitus (DM) were found to be associated with increased mortality as independent factors in logistic regression analysis, when all of these three factors were included in the model. Understanding the distinct clinical characteristics and the factors associated with mortality in patients with NF may lead to rapid diagnosis and improve the survival rates. Therefore, idiopathic NF is a crucial entity that requires serious suspicion for its diagnosis.