Reactive hemophagocytic syndrome.

Two cases of reactive hemophagocytic syndrome (RHS) are reported, and the clinical and pathological features are compared with other histiocytic proliferative disorders, including familial hemophagocytic lymphohistiocytosis (FHL) and malignant histiocytosis. RHS can be associated with a variety of infections, including viral, bacterial, fungal, and parasitic. RHS may also be familial as exemplified by our 2 cases in siblings. The isolation of an effective agent appears to be the only criterion by which a diagnosis of RHS can be made.