Cellulitis and necrotizing fasciitis can be distinguished by the depth of t
he cutaneous lesion and classically by the different bacteria implicated Th
is classification is not taken into account by the practitioner because of
a similar therapeutic strategy. That is why most authors used a single titl
e: necrotizing soft tissue infection. The potential severity of these infec
tions required a quick diagnosis to decrease the risk of mortality and seve
re functional consequences. The analysis of the literature doesn't allow to
establish the incidence of these infections. It was demonstrated that infe
ctions due to Streptococcus serogroup A increased over the last few years,
thanks to a specific surveillance system. Risk factors leading to these inf
ections are: cutaneous trauma, age, diabetes, varicella in children, contac
t with people infected by Streptococcus. The most recent studies demonstrat
ed a frequent polymicrobism of the infections, with anaerobes, Streptococcu
s, Staphylococcus, and gram-negative rods. At the onset of the disease, the
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 t
he depth of the infection and necrosis. Surgery will confirm the diagnosis
and allow for debridement of necrotized tissues. A delayed surgery increase
s the mortality risk factor; as stated in numerous studies. (C) 2000 Editio
ns scientifiques et medicales Elsevier SAS.