A 47-year-old male was admitted with a 5-day history of painful, red, swollen legs, and 48 hours of intermittent sweats and rigors. His only previous medical history was Perthe's disease of the right hip at the age of 8 years. He had no allergies and there was no family history. He was taking ampicillin at a dose of 500 mg t.d.s., as prescribed by his general practitioner. He had a temperature of 39°C on admission. Physical examination proved normal, apart from the area of skin over both ankles and the lower right leg, which was swollen, red, hot and tender.Initial investigations revealed leukocytosis of 15.9x10 -9 , neutrophils 11.7x10 -9 and a C-reactive protein level of 70.5 (normal range 0-10). Renal function and serum electrolytes were normal. Chest and ankle radiographs were also normal. Hip radiography revealed changes consistent with old Perthe's disease. Blood cultures were negative. A diagnosis of cellulitis was made by the admitting physicians, and the patient was prescribed intravenous benzylpenicillin and flucloxacillin.The leukocytosis resolved, but the patient continued to experience a fluctuating temperature. Nine days after admission, he developed non-specific abdominal pains. An ultrasound of the abdomen, kidneys and renal tract proved normal. The next day, he developed a rash on both legs (figure 1).