[Pathogenesis and morphology of hemophagocytic syndrome in the spleen]

Hemophagocytic syndrome (macrophage activation syndrome) is a group of disorders characterized by clinical, histological and biological symptoms of T-lymphocytes/NK cell-driven macrophage stimulation with subsequent hemophagocytosis which can be observed in various organs, particularly in the bone marrow and spleen. The main clinical symptoms include cytopenia, multiple organ dysfunction, fever unresponsive to antibiotics, hepatosplenomegaly and rash. Besides rare inherited immune system anomalies (primary hemophagocytic syndrome), the most prevalent etiologies of hemophagocytic syndrome are infections (viral, bacterial and parasitic), cancers, lymphoproliferative disorders and systemic diseases. Hemophagocytic syndrome is treated with immunosuppressives, cytostatic drugs, plasmapheresis and intravenous immunoglobulins/anti-TNF antibodies and due to the multiorgan involvement and the associated high mortality, recognition of early serum changes, such as very high levels of ferritin is mandatory. The most relevant histological changes are the increase of histiocytes showing evidence of phagocytosis of erythroid cells, platelets and granulocytes as well as in the spleen a rarefaction of the white pulpa with lack of lymph follicles and abundant lymphocytes, plasma cells and plasma cell precursors in the pulpa cords.