A previously healthy 36 year old woman with a remote history of infectious mononucleosis was seen by Rheumatology for intermittent high fever, rash, generalized weakness, pain and myalgia over the previous 2-3 months. Serological testing revealed Epstein Barr Virus (EBV) infection, possibly reactivation or past infection. She was diagnosed with adult-onset Still’s disease (ASD) and given standard treatment with steroids and analgesia. Six weeks following this presentation she deteriorated and was taken to hospital in unstable condition. She was intubated and admitted to the critical care unit. At that time it was recognized that she had not taken her treatment for ASD due to fear of the side-effect profile. On readmission, her blood work revealed elevated liver enzymes, albumin 10 g/L, INR 2.7, ferritin 38,080 ug/L, fibrinogen 1.1 g/L, triglycerides 1.98 mmol/L and creatinine 188 umol/L. A bone marrow aspirate was performed to rule out hemophagocytic syndrome (shown). Due to the history of hypotension, renal failure, liver failure, coagulopathy and hemophagocytosis in the bone marrow aspirate a diagnosis of macrophage activation syndrome (MAS) in ASD was made. In spite of aggressive efforts to resuscitate, she succumbed to her condition. MAS has a similar pathophysiology to reactive (secondary) hemophagocytic lymphohistiocytosis (HLH) and can be a life-threatening complication of adult onset Still’s disease (1). 1. Grom AA, Mellins ED (September 2010). Macrophage activation syndrome: advances towards understanding pathogenesis. Curr Opin Rheumatol 22 (5): 561–6.