Question category: Haematology
A 14 year old male attends his GP. He has noticed after playing football he appears yellow. He is currently unwell with a cold and has also noticed this yellow discolouration. On examination his sclerae are yellow. There is nil else of note on examination. There is no discolouration of his faeces or urine. Bloods reveal a bilirubin of 50 but other liver function tests are normal. The Hb is 14 g/l. The reticulocyte count is 25. Which of the following is the most likely diagnosis?