The term necrotising fasciitis comes from the words ‘necrosis’, which means death of a portion of tissue (flesh) and ‘fascia’, the name given to the sheets or bands of fibrous tissue which enclose and connect the muscles. NF is a severe infection involving the soft tissue below the skin, particularly the fascia. It can affect any part of the body but it is most common on the legs. On this page we ask ‘how does necrotising fasciitis happen?’
NF may be caused by a number of bacteria; one of these is Streptococcus pyogenes (also known as Strep. pyogenes or Group A streptococcus). Streptococcal necrotising fasciitis is a rare condition with approximately 1000 reported cases a year in the United Kingdom.
How does NF occur ?
NF arises most often spontaneously (without prior cause) in patients living in the community and often in previously perfect health. Cuts or grazes to the skin may be a source, but such damage may be trivial or may go unnoticed. Sometimes it may occur in hospitalised patients after surgery. When it arises in the community, the source is usually the patient’s own Strep pyogenes strain.
NF may begin in an established wound (following either injury or surgery) or in broken skin such as a leg ulcer. Excessive pain is an early warning symptom. Bacteria spreads very rapidly in the tissues below the skin surface, well ahead of any visible changes in the overlying skin.
Infection may progress at inches per hour
The patient rapidly becomes generally unwell, with progressive deterioration out of all proportion to the visible changes in the skin of the affected area. If not treated very quickly, the skin over the infected are becomes dusky and purple; blisters may form and the skin dies. By this stage, infection may have penetrated deep into the underlying tissues. Patients often develop shock, with collapse, low blood pressure, and failure of liver, kidneys and other vital systems.
Recent investigations have suggested that patients taking painkillers of the type known as ‘Non-Steroidal Anti-Inflammatory Drugs’ (NSAIDs), may be slightly more at risk of NF. This has yet to be proved. Other risk factors include diabetes, age over 50 years, steroid treatment, high blood pressure, obesity and alcoholism. Strep. pyogenes also appears to have a particular liking for the skin spots of chicken pox, and NF may occasionally complicate this infection.