Diagnosis: Acute necrotizing fasciitis
The patient was diagnosed with acute necrotizing fasciitis, a rare, often fatal, soft-tissue bacterial infection. According to the Centers for Disease Control and Prevention, only 500 to 1500 cases of necrotizing fasciitis are diagnosed each year in the US.1
Epidemiology
Peripheral vascular disease, diabetes, and a compromised immune system are significant risk factors for necrotizing fasciitis.2 Diabetes is present in 18% to 60% of cases;1,3 in addition, 19% to 77% of patients use intravenous drugs.1,3,4 Other significant predisposing factors include alcohol abuse (9%–31%),1,4 obesity,1,4 and malnutrition.3 Although risk factors are numerous, half of all cases of streptococcal necrotizing fasciitis occur in previously healthy individuals. Pathogenic agents can be introduced as a result of minor trauma, insect bites, or surgical incisions.
In this case the patient noted a “pimple” in the groin area and complained of pain for 5 days. By the time she reached the hospital she had mental status changes, fever, appeared toxic, and had signs of early septic shock. We can identify in this case the probable port of entry as the lesion in the groin that was visualized on physical exam to be draining pus.
Pathophysiology
Necrotizing fasciitis involves the superficial layer of skin, subcutaneous tissues, and fascia. The infection spreads rapidly along these layers, causing edema and compression of vasculature, which rapidly progresses to tissue necrosis and sepsis. Even with new broad-spectrum antibiotics, mortality can be as high as 75% in patients who become septic and develop renal failure.
Necrotizing fasciitis occurs when a mixed variety of organisms, both aerobic and anaerobic, invade the subcutaneous tissue and fascia.5 Most necrotizing soft-tissue infections are polymicrobial, with only a small percentage involving a single organism. In immune-compromised patients, Pseudomonas spp and gram-negative enteric organisms can be found. The organisms isolated most often in polymicrobial necrotizing soft-tissue infections are combinations of staphylococci (especially Staphylococcus epidermis with beta-hemolytic streptococcus), enterococci, Enterobacteriaceae spp (commonly Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, and Pseudomonas aeruginosa), streptococci, Bacterioides prevotella spp, anaerobic gram-positive cocci, and Clostridium spp.6
Patient presentation
The clinical history and a meticulous physical examination are essential in establishing an early diagnosis of necrotizing infections.5 Necrotizing fasciitis can be easily misdiagnosed as only cellulitis. Most often, a patient with necrotizing fasciitis appears ill, with constitutional symptoms of fever, chills, hypotension, dehydration, and rapid heart rate. You can also see erythema with bullae formation, serosanguineous fluids drainage, induration, and violaceous discoloration. Pain and crepitation may be noted.3,5,7 Rapid progression of edema and pain out of proportion to examination is seen in the early stages. The parts of the skin affected by the disease can become numb with progression of the infection; this is thought to be due to infarction of the cutaneous nerves located in necrotic subcutaneous fascia and soft tissue.5
Causative factors in this patient included diabetes and obesity. Diabetic neuropathy may have also delayed presentation and dulled her perception of pain. Diabetic microvascular disease may also have contributed to a faster progression of tissue hypoxia.