Adult-onset Still's disease complicated with hemophagocytic syndrome.

Hemophagocytic syndrome (HS) that occurs in the course of adult-onset Stills disease (AOSD) has been reported only rarely in the literature. HS and AOSD share overlapping clinical and laboratory features, therefore, it is difficult to recognize HS as a complication of AOSD. Here, we report the case of a 46-year old woman with classical features of AOSD. Severe pancytopenia and jaundice associated with extreme hyperferritinemia occurred during high-dose steroid treatment. Bone marrow biopsy showed typical pathological features of hemophagocytosis, which confirmed the coexistence of HS with AOSD. The patient was treated with methylprednisolone pulse therapy of 500 mg/day for 3 days, as recommended in cases of HS complicating AOSD, and her condition improved gradually. During the disease course, extensive studies could not identify any viral infection or other known underlying etiology for the reactive hemophagocytosis. Currently, the patient is in remission on low-dose prednisolone and azathioprine.