Fever without a source: evolution of a diagnosis from Kawasaki disease to acute myelogenous leukaemia

A previously healthy 11-month-old male patient presented with fever, abdominal pain and irritability. As part of an extensive evaluation for the cause of his fevers, an echocardiogram was performed and showed mildly dilated coronary arteries, leading to a diagnosis of incomplete Kawasaki disease (KD). He was treated with intravenous immunoglobulin (IVIG), defervesced and was discharged home. Two weeks later, he presented with anaemia initially attributed to haemolytic anaemia secondary to IVIG and received a red blood cell transfusion. However, his anaemia recurred 2 weeks later with leucocytosis, prompting a bone marrow aspirate 4 weeks after his diagnosis of KD. This demonstrated acute myelogenous leukaemia most consistent with acute megakaryocytic leukaemia. This case highlights the potentially subtle presentation of acute leukaemia and the need to keep an open mind and reconsider the initial diagnosis as new information comes to light in the care of an ill child.