Haemophagocytic lymphohistiocytosis secondary to viral infection is an unusual but well recognised cause of bone marrow dysfunction and multiple organ failure in young patients. Two 18 year-old patients were admitted to a tertiary liver unit with features of acute liver failure, cardio-respiratory collapse and pancytopenia. Serological tests and bone marrow examination with in-situ hybridisation revealed severe acquired haemophagocytic lymphohistiocytosis secondary to acute Epstein-Barr virus infection. Both patients died despite full supportive therapy; the first due to pulmonary haemorrhage, the second due to acute respiratory distress syndrome refractory to high frequency oscillatory ventilation. The clinical spectrum, diagnostic features and current evidence based recommendations for treatment of this condition are explored. The diagnosis of haemophagocytic lymphohistiocytosis should be considered in young patients with marked bone marrow dysfunction and multiple organ failure. Further research into appropriate therapy for patients with acute severe forms of the disease who require intensive organ support is required.