Pathogenesis of FG is multifactorial and commonly begins as cellulitis or an untreated purulent infection that progresses through enzymatic and platelet reactions, eventually culminating in microthrombotic changes within local subcutaneous veins.2,4,8  This in turn causes an alteration in the delivery of oxygen to the tissues, which allows for development of irreversible necrosis.2,4 FG is able to progress rapidly in these conditions in which ischemic changes result from microvascular constriction in susceptible disease states.4

FG is frequently a polymicrobial infection, and the microbes most commonly implicated in its development are Escherichia coli and Bacteroides, and clostridial, staphylococcal, and streptococcalspecies.2,4,7,8  Streptococcal and staphylococcal species are known to produce enzymatic reactions that alter host immunity, resulting in degradation of the host’s connective tissue structures and a more rapidly progressive disease state.8,10 Anaerobic bacteria, though more rare than their aerobic counterparts, thrive in this oxygen-deficient environment and create a synergistic effect that perpetuates the fulminant progression of the disease.10,11 These anaerobic organisms subsequently release their own characteristic enzymes that increase intravascular coagulation, resulting in progressive ischemia.9,10,11  

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As the infectious process progresses from the initial site of inoculation, FG classically traverses the planes of Colles fascia and the perineum with predictable ease and may ultimately affect the distal thighs and abdominal wall.2,4 Infrequent cases of extension to the clavicles have been reported in instances when the disease was able to progress undetected until late stages.2,9,11,13 The testicles are often spared in the progression of necrosis due to a separate blood supply from the aorta.9,11

Signs and Symptoms

Associated with a myriad of symptoms, FG can easily remain clinically elusive. It has been reported that patients with FG can present early in the course of the disease with nonspecific symptoms of mild, focal swelling and pain in the groin and perineum.7,8,15   Systemic symptoms of fever and nausea are often lacking in early disease. In late stages, pain often becomes more pronounced; men may complain of swelling, and patients may report systemic symptoms such as fever.7,8,10,15  However, the systemic symptoms are unreliable, with fever being present in 20% of confirmed cases of FG. Its absence therefore does little to rule out early- through late-stage disease.15

Physical Examination

Early stages of FG can begin as a focal area of erythema within the perineum and groin with often limited systemic response. Although tachycardia has been observed, findings most consistent with uncomplicated cellulitis typically are present.7,8,9-11,16 In late stages the disease becomes more consistent with expanding erythema, hemorrhagic bullae overlying tense skin with palpable crepitus (when gas-producing organisms are present), pain out of proportion to clinical findings or anesthesia, fever, and signs of septic shock including hypotension and tachycardia (Figures 1-2).2,7-9,13 As with symptoms of FG, these physical examination findings are more specific than sensitive, being present in <40% of cases, so their absence does not preclude the presence of disease.8,11,16 During the final stages of FG, patients may develop multiorgan failure, including acute respiratory distress syndrome and disseminated intravascular coagulopathy.11 Therefore, it is incumbent upon clinicians to consider FG in all patients with risk factors even in the absence of notable physical examination findings, in particular those that are refractory to conservative outpatient treatment.2,10

Figure 1. Fournier gangrene of the scrotum.

Figure 2. Fournier gangrene of the scrotum.