Bone marrow biopsy in hemophagocytic syndrome

Aims: Hemophagocytic syndrome (HPS) is a severe and acute clinical event occurring with fever, hepatosplenomegaly, and pancytopenia due to uncontrolled phagocytosis of blood cells and precursors. Although HPS represents a secondary phenomenon, it can mask the underlying condition, generally a neoplastic or infective disease, thus making the patient management rather difficult. The aims of this study were to point out the main pathological features useful to highlight the primary disease and show the eventual discrepancies among the different cases. Methods and results: Bone-marrow biopsies (BMBs) of 26 patients with HPS were morphologically and immunophenotypically evaluated; the patients were 12 females and 14 males with mean age of 45.8 years (range 18-80 years). Fifteen patients had a hematological neoplasia either at onset (13 cases) or relapse (2 cases); 5 patients had evidence of active infection immediately prior to HPS development, whereas in 6 patients no definite etiology was established. Cases were therefore divided into neoplasia related, infection related, and "idiopathic". In all cases BMB showed marked histiocyte hyperplasia with hemophagocytosis. In cases of bone-marrow lymphoma or leukemia involvement, immunohistochemistry allowed diagnosis of the underlying disease to be made; infection-related cases showed a reactive marrow with mature interstitial T-lymphoid infiltration, whereas in idiopathic cases T cells were mainly aggregated in small clusters. In no cases were significant percentages of natural-killer (NK) cells detected. Interpretation and conclusions: Although no strict morphological or immunophenotypical criteria able to allow an immediate diagnosis of underlying disease were pointed out, in most cases BMB proved to be an essential and reliable diagnostic tool. According to our experience, when HPS occurs, the first diagnosis to investigate is a neoplastic disease which sometimes can be latent or hidden.