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INTRODUCTION

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SUMMARY

Diseases of the histiocyte (i.e., macrophage or dendritic cell) lineage can be divided into four groups based upon the final maturation steps from their myeloid progenitor cells: (1) Langerhans cell histiocytosis (LCH), (2) malignant histiocytoses or dendritic cell sarcomas, (3) juvenile xanthogranuloma/Erdheim-Chester disease, Rosai-Dorfman disease, and (4) hemophagocytic lymphohistiocytosis syndromes. Storage diseases of macrophages are discussed in Chap. 72. The distinction among these diseases is based upon clinical characteristics and histopathologic staining for unique surface markers. LCH may present at birth or in adulthood with skin rash, bone pain, draining ears, oral ulcers, gingivitis, pulmonary dysfunction, chronic diarrhea, diabetes insipidus, and marrow or liver failure. Therapy for LCH in children has been studied in clinical trials by the Histiocyte Society. Treatment for adults is based primarily on case series. Although relapses are not typically rapidly fatal, they are associated with a higher risk of endocrine and central nervous system complications. The diagnostic criteria for the malignant histiocytosis have been clarified by cell-surface marker studies. Treatment options and prognosis vary widely. Erdheim-Chester disease and juvenile xanthogranuloma are phenotypically similar, but are treated differently. Erdheim-Chester disease is found almost exclusively in adults and juvenile xanthogranuloma occurs primarily in children. Rosai-Dorfman disease presents with massive cervical lymphadenopathy in most patients, but may also involve other parts of the body. There are several treatment options for Rosai-Dorfman disease, Erdheim-Chester disease, and juvenile xanthogranuloma, but no clinical trials of specific drugs have been published. Hemophagocytic lymphohistiocytosis (HLH) is characterized by pathologic inflammation and may present with infections, hepatitis, meningitis, or autoimmune diseases. Without therapy, HLH is almost universally fatal. Most patients who receive prompt diagnosis and treatment with immune suppression therapy survive.

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Acronyms and Abbreviations

AHSCT, allogeneic hematopoietic stem cell transplantation; ALL, acute lymphoblastic leukemia; ATG, antithymocyte globulin; CD, cluster designation; CT, computed tomography; DC, dendritic cell; DI, diabetes insipidus; DLCO, diffusing capacity in lung for carbon dioxide; ECD, Erdheim-Chester disease; FEV1, forced expiratory volume in 1 second; HLA-DR, human leukocyte antigen-D related; HLH, hemophagocytic lymphohistiocytosis; IFN, interferon; IL, interleukin; JXG, juvenile xanthogranuloma; LC, Langerhans cell; LCH, Langerhans cell histiocytosis; M-CSF, macrophage colony-stimulating factor; MRI, magnetic resonance imaging; NK, natural killer; PET, positron emission tomography; RDD, Rosai-Dorfman disease.

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CLASSIFICATION OF THE HISTIOCYTOSES

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The general description of cells in the monocyte-macrophage system (mononuclear phagocyte system) has been largely clarified (Chaps. 67 to 69), although some ambiguity remains. Nomenclature committees remain loyal to the term “histiocyte,” a designation assigned in the 19th century to tissue macrophages, although the “histiocytosis” umbrella includes functional and neoplastic disorders of a broad range of cells in the monocyte, macrophage, and dendritic cell (DC) lineages. The distinctions among diseases in this category are determined by (1) clinical findings, (2) histopathology, (3) immunocytology to define the antigens on the surface of the pathologic cells, and (4) cytogenetic or genetic features (Table 71–1).

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