The pathogenesis of Fourniere's Gangrene is usually through a localised small infective focus overwhelming the local inflammatory and immune response. Consequently, virulent organisms are most frequently isolated in the presence of some form of immunocompromise. Typically, the infection is polymicrobial and involves:
- Streptococcal species and particularly beta haemolytic streptococci
- Staphylococcal species
There is thought to be a synergy between the infecting organisms eg one organism produces enzymes to thrombose perforating skin vessels while another produces enzymes to break down the fascia. Consequently, a fascial necrosis propagates beneath the skin with subsequent skin infarction and late muscle necrosis.