A 10-year-old, 45 kg boy with a background of sickle cell disease had presented to his local A&E with a 5-day history of abdominal pain, and a more recent 2-day history of back and shoulder pain. The morning of the presentation, he had started vomiting and was noted to be jaundiced by his accompanying parent. His mum reported he normally had a haemoglobin of 80–90 g/L and he had had no in-patient hospital stays previously.