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A 66-year-old male with newly diagnosed hepatic diffuse large B-cell lymphoma (DLBCL) presented with neutropenia and anemia. A staging bone marrow biopsy and peripheral blood smear demonstrated hemophagocytosis (Figure 1).  No marrow involvement of DLBCL was found by flow cytometry or immunohistochemistry.  These findings led to a diagnosis of hemophagocytic lymphohistiocytosis (HLH) based on the following criteria: fever ≥ 38.5°C, hypertriglyceridemia, low peripheral blood counts, and hemophagocytosis in bone marrow, spleen, or lymph node.  Hemophagocytosis is a rare finding in the peripheral blood.  When identified, its presence should prompt an investigation into HLH. Hemophagocytic lymphohistiocytosis can be primary or secondary. Primary (familial) HLH is an autosomal recessive disorder caused by a mutation in perforin (PRF1), MUNC, or Syntaxin 11 (STX11). These mutations impair the cytotoxic function of cytotoxic T-cells and natural killer (NK) cells. Primary hemophagocytic lymphohistiocytosis is also associated with inherited immunodeficiency syndromes, such as Chediak-Higashi syndrome. Secondary HLH is often due to malignancy, autoimmune disease, and Epstein Barr virus (EBV) infection. These conditions lead to dysregulated immune system function. In this case, the patient’s diagnosis of hemophagocytic lymphohistiocytosis was secondary to previously diagnosed diffuse large B-cell lymphoma.