Adult onset Still's disease associated hemophagocytosis.

Reactive hemophagocytosis is characterized by the activation of histiocytes with prominent hemophagocytosis in the reticuloendothelial system, and usually occurs in association with underlying disorders such as viral or bacterial infection and malignancy. We describe 3 cases of adult onset Still's disease (AOSD) who developed hemophagocytosis in bone marrow. Extensive studies could not identify any viral infection or other known underlying disorders for reactive hemophagocytosis except for active AOSD. Although the causative mechanisms of reactive hemophagocytosis in AOSD are not clear, our cases suggest the possibility of AOSD associated hemophagocytosis.