Adult onset Still’s disease (AOSD) is a systemic inflammatory disease of unknown etiology and pathology characterised by polyarthritis, intermittent high fever and typical skin rashes. On rare occasions AOSD may manifest itself as hemophagocytic syndrome (HPS) or fulminant hepatitis. In this paper we describe a 23-year-old male patient pathologically determined to have HPS and fulminant hepatitis, and whom we diagnosed with AOSD while being followed up for fever of unknown origin and investigated for fever, hepatosplenomegaly and pancytopenia, and on whom we performed splenectomy during the diagnosis and treatment stage. In the light of knowledge in the literature and the fatal course followed by our case we are of the opinion that AOSD follows a more fatal course in the presence of HPS or fulminant hepatitis, and that aggressive treatment will be appropriate in such cases.