Gas gangrene (Clostridium perfringens)

What it is

Clostridium perfringens turns up in two very different places, and the exam uses both: as an infection in the skin around a fracture site, and as a cause of food poisoning.

The wound infection, and how it is recognised

The stereotypical history for infection by C. perfringens is a middle-aged man who sustains an open fracture of his leg and then develops painful, oedematous, bronze coloured skin around the fracture site, with haemorrhagic blebs and bullae, and crepitus and tenderness on palpation of the affected skin.

Four things in that line carry it: the open fracture, the bronze colour, the blebs and bullae, and crepitus on palpation.

The same words are also set out as the typical history of necrotizing fasciitis, so one picture carries both names, and a question may ask it under either.