Perturbations biologiques et immunologiques au cours des syndromes hémophagocytaires

Hemophagocytic lymphohistiocytosis (HLH) is the consequence of immune system hyperactivation, responsible for an hyperinflammatory state potentially fatal. Lymphocytes and histiocytes hyperactivation is characterised by a pro-inflammatory cytokine storm : massive secretion of IL-1, IL-6, TNF-α, IFN-γ by activated lymphocytes and macrophages. Cytokine hypersecretion is responsible for clinical and biological signs. Genetic (primary HLH) or acquired (secondary HLH) defect of CD8 T lymphocyte and NK cell cytotoxicity is at the origin of HLH. Secondary or acquired HLH occurred in infections, autoimmune diseases or malignancies. HLH symptoms are not specific, and diagnosis is often delayed. Biological parameters are cytopenias, hyperferritinemia, hyperetriglyceridemia, hypofibrinogenemia, hemophagocytosis in bone marrow or other involved organs. Advances in pathophysiological mechanisms understanding allow to identify perturbed immunologic parameters : sCD25 and sCD163 increased, CD8 T cell HLA-DR overexpression, NK cytotoxicity absent or decreased. Initial treatment is urgent and consists of a decrease of hyperinflammatory state. Hematopoietic cell transplantation is proposed in genetic HLH.