The histiocytic disorders: a pathophysiologic analysis.

The histiocytoses are a diverse group of disorders involving cells of the mononuclear phagocyte series. These diseases are usually characterized by proliferation and activation of macrophages caused either by external stimuli or by an intrinsic cellular abnormality. We propose that these conditions be classified as reactive histiocytosis (inciting agent known or unknown), lipid storage disorder, and mononuclear phagocyte neoplasia based on apparent cause and natural history. Recent knowledge of monocyte-macrophage development and function allows for construction of pathophysiologic models of diseases formerly approached in a descriptive fashion. Macrophage activation appears to mediate many clinical features of th histiocytic disorders, such as hemophagocytosis, fever, and osteolysis. Further understanding of the pathogenesis of the histiocytic disorders should lead to improved therapy.