Upper leg discomfort following a bout of sore throat and flu.

A 72-year-old woman with a history of diabetes mellitus and renal dysfunction has had a light red, moderately painful spot on her left thigh for four weeks. The spot developed after an episode of sore throat and flu symptoms.

She has had a fever of up to 42 °C for four days and the spot on the upper leg is increasingly painful. When she woke up in the morning, the skin “jumped open.” The GP saw a sick patient with a high fever and a large, partly purple discolored abnormality on the left upper leg. He sent her to the ER.