A 10 year old Ghanaian girl presented to the accident and emergency department of her local hospital with a one week history of fever, increasing shortness of breath and chest pain. She was known to have sickle cell disease and her mother thought that she might be having a sickle cell crisis. On examination she had the following abnormalities:

• a temperature of 39.5° C, jaundice and mild cervical lymphadenopathy

• tachypnoea, an oxygen saturation of 88% in air, reduced breath sounds and fine crepitations in her left lower lobe

• raised jugular venous pressure, tachycardia and normal heart sounds

• hepatomegaly (3 cm).

She was admitted to hospital. The results of initial investigations are shown in table 1. In addition a blood culture was taken. A chest x ray (fig 1) was thought to show cardiomegaly and bilateral hazy shadowing. She was started on antibiotic treatment with intravenous cefotaxime for a presumed chest infection.

The paediatric registrar thought that the most likely diagnosis was a chest infection but was concerned about a possible sickle cell crisis. He interpreted the cardiomegaly as being caused by chronic anaemia. He discussed the situation with the consultant haematologist who thought that some of the clinical features were consistent with this diagnosis, but that the blood film and normal lactate dehydrogenase concentration were not. Also, her fetal haemoglobin was known to be 11% and a sickle cell crisis is unlikely if the proportion of fetal haemoglobin is greater than 9%. Nevertheless, the importance of avoiding hypoxaemia was stressed and a blood transfusion to improve her haemoglobin to 8 g/dl was recommended.

The following day the patient was no better. She remained pyrexial, tachycardic and tachypnoeic. There was no growth on …