[Hemophagocytic lymphohistiocytosis—a contemporary medical problem]

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening disorder of immnoregulation caused by various inherited and acquired factors. Uncontrolled activation of T lymphocytes and macrophages, together with an impaired cytotoxic function of NK cells, results in the massive cytokine release and hyperinflammatory phenotype. HLH is characterized by fever, splenomegaly and peripheral blood cytopenia. Cytohistological examination shows accumulation of lymphocytes and macrophages, sometimes with hemophagocytic activity, in different tissues (e.g., bone marrow). Laboratory findings include hyperferritinemia (often 'sky-high' > 10.000 microg/l), hypertriglyceridemia, hypofibrinogenemia, and high levels of the alpha chain of the soluble interleukin-2 receptor (sIL-2R also called sCD25). In 2004 The Histiocyte Society updated current diagnostic guidelines for HLH. Therapy of HLH is based on suppression of the hyperinflammatory status by destruction of activated CD8+ T lymphocytes and macrophages, and treatment of any existing HLH triggers. However, treatment of HLH is associated with high morbidity and mortality. Therefore consideration should be given to referring HLH patients to centers with experience in the treatment and care of those with HLH. Due to aggressive course, awareness of HLH signs and symptoms is crucial among physicians for the early diagnosis and immediate introduction of adequate HLH treatment.