Introduction
Necrotising fasciitis (NF) is a life-threatening infection which can affect the skin, subcutaneous tissue, superficial and deep fascia with muscular extension1. Predisposing factors for developing NF include chronic immunocompromised states, prolonged corticosteroid use, diabetes mellitus and intra-venous drug use1.
NF originating in and affecting the head and neck region is rare1. NF has been documented in patients with dental infections, traumatic neck wounds and deep space neck infections1. Peri-ocular NF is very rare, with a rate of 0.24 cases per million per annum2. Mortality rates of NF can exceed 50%, with peri-ocular NF mortality ranging from 3-10%2,3.
The pathophysiological mechanism behind NF includes the seeding and proliferation of a bacterial pathogen in the subcutaneous tissue and fascial layers. This pathogen triggers the release of inflammatory mediators, including toxins and cytokines2. This inflammatory cascade results in microthrombi formation heralding ischaemic necrosis of tissue. Severe pain, erythema, bullae formation, and surgical emphysema with systemic sepsis are hallmark features which should raise suspicion.
Four types of necrotising fasciitis have been described in the medical literature, with types 1 and 2 the most prevalent3. Type 1 NF is a polymicrobial infection usually consisting of mixed anaerobes and aerobes acting in a synergistic fashion3. Type 1 can account for up to 80% of all necrotising fasciitis cases3. Type 2 usually has a monomicrobial aetiology, with Group A beta-haemolyticStreptococcus (GAS) as the most prevalent pathogen3. Type 2 NF accounts for 20-30% of all cases of necrotising fasciitis, and can present as aggressive and rapidly progressing. GAS can induce a large inflammatory response by reducing phagocytic function and interferon secretion. Type 2 NF is more likely to produce bacteraemia with streptococcal toxic shock syndrome4. Type 3 NF is mono-microbial and usually gram negative in origin with Type 4 NF occurring in immunocompromised patients and is usually fungal in nature4.
Management of necrotising fasciitis requires prompt recognition, intravenous anti-microbials and urgent surgical debridement.