We present the case of a 10 month old infant with trisomy 21 that was admitted to the Paediatric Intensive Care Unit with respiratory deterioration secondary to respiratory Syncytial Virus Bronchiolitis. At the time he was on maintenance chemotherapy for low risk down syndrome associated acute myeloid leukaemia. He had never had thoracic surgery but spontaneously developed bilateral, large volume pleural effusions confirmed to be chylothoraces. Investigations into the causation of the chyle leak proved fruitless, the likeliest diagnosis being a delayed presentation of down syndrome associated congenital chylothorax. Despite conventional management with pleural drainage in excess of 1500 ml a day, cessation of enteral feeding, initiation of total parenteral nutrition and an octreotide infusion for over two months the patient did not survive. We focus on the diagnostic challenges associated with paediatric childhood chylothoraces, the pathophysiological effect on nutritional status and the available conventional therapies.