Haematology Vignettes – 30

A case of necrotising fasciitis in a 56 year old male.

A 56 year old male was transferred from a regional hospital to the intensive care ward at the Prince of Wales Hospital. He had extensive necrosis extending from the scrotum to his flank, axilla, and shoulder and spreading along his arm. He had necrotising fasciitis and was to have surgical debridement. He was too unwell for the Hyperbaric Chamber.

A full blood count was received in the laboratory. The results were as follows:

Hb 89 RR (130-180) g/L
Hct 0.262 RR (0.40-0.54)
MCV 87.9 RR (80-100) fL
MCH 29.9 RR (26.5-33.0) pg
WBC 39.9 RR (3.5-11.0) x 10 9/L
Plats 80 RR (150-400) x 10 9/L

The blood film showed an absolute neutrophilia with marked toxic granulation; moderate numbers of microspherocytes and thrombocytopenia. These features are classically found in Clostridium perfringens infection. This was a case of severe septicaemia and haemolysis secondary to necrotising fasciitis. See figure 1.

The term necrotising fasciitis describes a condition of rapidly spreading infection, usually located in fascial planes of connective tissue resulting in tissue necrosis. Fascial planes are bands of connective tissue that surround muscles, nerves and blood vessels. The speed with which necrotising fasciitis spreads is directly proportional to the thickness of the subcutaneous layer.

Many types of bacteria can cause necrotising fasciitis ( e.g., Group A streptococcus (Streptococcus pyogenes), Staphylococcus aureus, Clostridium perfringens, Bacteroides fragilis, Aeromonas hydrophila). The disease is classified as either Type I (polymicrobial) caused by a number of different organisms or Type II (monomicrobial) caused by a single organism. The causative organism may be aerobic or anaerobic.
The frequency of necrotizing fasciitis has been on the rise due to an increase in immunocompromised patients with diabetes mellitus, cancer, alcoholism, vascular insufficiencies, organ transplants, HIV infection and also occurs in patients with neutropenia
The mean age of a patient with necrotizing fasciitis is 38-44 years. The disease rarely occurs in children. Paediatric cases have been reported from resource-poor nations where poor hygiene is prevalent.

The patient in this case study was diagnosed with Clostridium perfringens induced necrotising fasciitis. Clostridium perfringens is a saprophytic organism inhabiting the bowel and genital tract. It has no pathological significance in the absence of clinical infection. Clostridium perfringens produces at least 12 antigenic protein toxins, the most common of which is the alpha toxin. These toxins react with lipoprotein complexes on cell surfaces, liberating potent haemolytic substances known as lysolecithins which result in cell lysis, hence the presence of microspherocytes on the blood film. This process leads to a severe haemolytic anaemia. Acute renal and hepatic failure develops leading to death in as short a period as 12 hours if not treated immediately.

The Chemistry results on this case were as follows:

Urea 10.1 mmol/L RR (2.9-7.1)
Creatinine 152 umol/L RR (60-110)
Bilirubin total 47 umol/L RR (0-25)
ALP 106 U/L RR (38-126)
GGT 71 U/L RR (0-50)
AST 89 U/L RR (<45)
ALT 72 U/L RR (<45)

The basis of treatment is surgical debridement of necrotic tissue and antibiotic therapy. In severe infections, hyperbaric oxygen is an important adjunct in the treatment of necrotising fasciitis. Massive doses of benzyl penicillin are administered intravenously. Should the patient be allergic to penicillin, metronidazole is effective in high doses.

The patient in this case study died within 24 hours of having been admitted into the ICU ward.