[Hemophagocytic lymphohistiocytosis: diagnostic problems in pediatrics]

Hemophagocytic lymphohistiocytosis (HLH), also known as hemophagocytic syndrome (HS), is a life-threatening hyperinflammatory condition caused by uncontrolled proliferation of activated lymphocytes and histiocytes producing excessively proinflammatory cytokines. HLH can occur in all age groups. The most common syndromes are: prolonged fever, hepatosplenomegaly, unspecific neurological symptoms, pancytopenia, hemophagocytosis. Characteristic biochemical markers include high triglycerides, ferritin and decreased fibrinogen. There are two forms of HLH, primary (genetic) and acquired (secondary to infections, malignant and autoimmune diseases). Occurrence of both forms of HLH, acquired and genetic, is induced by infections, usually viral or by other triggering agents. Despite established diagnostic criteria many cases probably remain unrecognized. The main diagnostic difficulty is low specificity of symptoms, and in secondary form contemporary occurrence of symptoms of underlying disease. The aim of HLH treatment is to suppress hyperinflammation, what can be achieved by use of immunosuppressive/immunomodulating agents or cytostatics. Patients with genetic form of HLH require hematopoietic stem cell transplantation. Awareness of the symptoms and diagnostic criteria of HLH is important for early diagnosis and immediate application of life-saving therapy.