Skin and soft tissue infections can be classified into purulent and nonpurulent ones.
Non-purulent ones are those without associated pus. Purulent ones are those associated with pus.
Picture of non-purulent skin and soft tissue infections:
Picture of purulent skin and soft tissue infections:
Skin and soft tissue infections can be categorized in terms of severity as uncomplicated, complicated but non-necrotizing complicated, and necrotizing fasciitis.
Uncomplicated SSTIs include superficial cellulitis, folliculitis, furunculosis, simple abscesses, and minor wound infections. These infections respond well to either source control management (ie, drainage or debridement) or a simple course of antibiotics. These infections pose little risk to life and limb.
Complicated SSTIs involve the invasion of deeper tissues and typically require significant surgical intervention. The response to therapy is often complicated by underlying disease states. Complicated SSTIs include complicated abscesses, infected burn wounds, infected ulcers, infections in diabetics, and deep-space wound infections. They are often limb- or life-threatening.
Necrotizing fasciitis is a progressive, rapidly spreading, inflammatory infection that is located in the deep fascia and is associated with secondary necrosis of the subcutaneous tissues. The inflammation of the deep fascia causes thrombosis of the dermal vessels, and it is this thrombosis that is responsible for the secondary necrosis of the overlying subcutaneous tissue and skin.
The above classification and severity categorization are helpful as guides in management.
Infectious Disease Society of America