Primary Hemophagocytic Lymphohistiocytosis and Macrophage Activation Syndrome: The Importance of Timely Clinical Differentiation

Hemophagocytic lymphohistiocytosis (HLH) is a potentially fatal hyperinflammatory syndrome caused by excessive activation and expansion of T lymphocytes (predominantly CD8-positive) as well as macrophages that exhibit hemophagocytic activity.1-3 More than 90% of almost 3000 articles on HLH have been published within the last decade. Initially, HLH was described as a group of rare autosomal-recessive immune disorders of early childhood.1 HLH has been recognized as both a familial disorder (primary hemophagocytic lymphohistiocytosis [pHLH]) and as a sporadic one that usually is referred as secondary hemophagocytic lymphohistiocytosis (sHLH).

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