A diagnosis not to miss

A 45-year-old woman attended accident and emergency after fainting and feeling unwell with a fever. Blood and protein were noted in the urine. A diagnosis of urinary tract infection was made and she was sent home with antibiotics. She became increasingly unwell with fever, headache and confusion before collapsing the following day. On examination her Glasgow Coma Score was 7/15, with a fever of 38.2° C, respiratory rate of 35/minute, pulse of 120/minute and blood pressure of 160/95 mmHg. She had a widespread petechial rash. Tone was increased in all four limbs and she had extensor plantar responses. There was no neck stiffness. Her pupils were equal and reactive, but her gaze deviated to the right. Soon afterwards she had a focal fit involving the left side of her body. Her blood results were: sodium 142 mmol/litre, potassium 2.8 mmol/litre, urea 9.1 mmol/litre (blood urea nitrogen 25.3 mg/dl), creatinine 120 mmol/litre (1.44 mg/dl), glucose 12.5 mmol/litre (208 mg/dl), haemoglobin 7.7 g/dl, total white cells 21.8 × 10 9 /litre (neutrophils 14.2 × 10 9 /litre), platelets 8 × 10 9 /litre. Arterial blood gases and coagulation studies were normal. A contrast computed tomography scan of the brain, performed under general anaesthesia, was normal.