Cellulitis and necrotizing fasciitis can be distinguished by the depth of t
he cutaneous lesion and classically by the different bacteria implicated. T
his classification is not taken into account by the practitioner because of
a similar therapeutic strategy. That is why most authors used a single tit
le: necrotizing soft tissue infection. The potential severity of these infe
ctions required a quick diagnosis to decrease the risk of mortality and sev
ere functional consequences. The analysis of the literature doesn't allow t
o establish the incidence of these infections. It was demonstrated that inf
ections due to Streptococcus serogroup A increased over the last few years,
thanks to a specific surveillance system. Risk factors leading to these in
fections are: cutaneous trauma, age, diabetes, varicella in children, conta
ct with people infected by Streptococcus. The most recent studies demonstra
ted a frequent polymicrobism of the infections, with anaerobes, Streptococc
us, Staphylococcus, and gram-negative rods. At the onset of the disease, th
e diagnosis is difficult to establish. Pain, induration of tissues, a rapid
evolution, the inefficacy of antibiotic treatment suggest the diagnosis of
necrotizing infection. MRI, when available, is a good technique to reveal
the depth of the infection and necrosis. Surgery will confirm the diagnosis
and allow for debridement of necrotized tissues. A delayed surgery increas
es the mortality risk factor, as stated in numerous studies.