SKIN AND SKIN structures are among the most frequent sites of human bacterial infection and account for ~10% of hospital admissions in the United States.

The terminology used for infections of skin and skin structures is often confusing. “Primary” skin infections occur in otherwise normal skin and are usually caused by group A streptococci or Staphylococcus aureus. Infections are called “secondary” when they complicate chronic skin conditions (e.g., eczema or atopic dermatitis).

A second classification system divides skin and skin-structure infections into “uncomplicated” or “complicated,” the latter defined as involving abnormal skin or wound infections occurring in a compromised host or requiring substantial surgical intervention.

A more important and, for our purposes, relevant distinction with essential management implications subdivides soft-tissue infections into “non-necrotizing” and “necrotizing” processes. This chapter reviews only the necrotizing soft-tissue infections (NSTIs) – the ones that pose real emergencies that are rapidly progressive, destructive, and highly lethal.

NSTIs can be defined as infections of any of the layers within the soft-tissue compartment (dermis, subcutaneous tissue, superficial fascia, deep fascia, or muscle) that are associated with necrotizing changes. NSTIs are typically not associated with abscesses, although they can originate from an untreated or inadequately drained abscess.