Life threatening infective necrosis of superficial tissue fascia, often more extensive than would be suspected by appearance of overlying skin.  Can start in previously normal skin, with an insignificant entry site!

Group A streptococcus mostly, but can be polymicrobial especially in immunocompromised.

The top three early presenting clinical features are swelling, pain and erythema but these are entirely non-specific, so initial misdiagnosis common (almost three-quarters of patients in 1 review). More specific features are:

• pain out of proportion to the physical findings;
• failure to improve despite broad-spectrum antibiotics;
• presence of bullae in the skin; and gas in the soft tissue on plain X-ray.

Other possible characteristics described:

• tense oedema extending beyond margin of erythema
• loss of sensation
• LRINEC score in adults based on lab criteria (high glucose, high creatinine, high CRP, high WCC, low sodium, low Hb) has 76% sensitivity, NPV 88.1%.

Early surgical exploration is the best approach in the uncertain case; and early surgical debridement is key to control. IVIG may be of benefit.

Notifiable in Scotland.