Pathogenesis of Hemophagocytic Lymphohistiocytosis.

Hemophagocytic Lymphohistiocytosis (HLH), an inherited life-threatening inflammatory disorder, has gained growing recognition not only in children but also increasingly in adults over the past 2 decades. HLH involves inborn defects in lymphocytes, which normally mediate control of infectious and inflammatory conditions within the immune system and in other tissues. In the context of inherited defects in cytotoxic cells and other immune cells, the disorder is classified as familial or primary HLH. Secondary HLH occurs in the settings of infections or underlying rheumatologic disorders. Secondary HLH also accompanies some lymphoid malignancies.