MRCP2-2419

A 42-year-old man presents to the haematology day unit 55 days after receiving a bone marrow transplant from his sibling for acute myeloid leukaemia. He has been doing well until he noticed dark urine three days ago, followed by a fever and confusion. On examination, he has a high temperature, rapid pulse, and yellow sclerae. His blood tests show low haemoglobin and platelet counts, reactive white cells, and elevated levels of creatinine, bilirubin, and lactate dehydrogenase. His ciclosporin level is also high. What is the most likely diagnosis?