Syndromes of inappropriate macrophage activation in childhood.

The concept of inappropriate macrophage activation (IMA) embraces the clinicopathologic conditions associated with non-malignant lymphohistiocytic proliferation: familial lymphohistiocytosis (FLH) and hemophagocytic syndromes associated with viral, bacterial, fungal or parasitic infections in both immunodeficient and immunocompetent patients. IMA is also observed during the clinical course of primary immunodeficiencies (Chediak Higashi). The mechanisms of IMA are still unknown. Prognosis varies according to the immune status of the patients but is often very poor. Steroids but principally VP16-213 can slow the macrophage hyperactivation. Allogenic bone marrow grafting is indicated in FLH.