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The histiocytic syndromes are clinically heterogeneous disorders that result from an abnormal proliferation of histiocytes—either monocyte-macrophages (antigen-processing cells) or dendritic cells (antigen-presenting cells). Classifying these disorders is difficult and has changed over time as an understanding of the biology of these cells has evolved (see Table 1: Histiocytic Syndromes: The Histiocytic Syndromes for the current classification system). Langerhans' cell histiocytosis, a dendritic cell disorder, is discussed below. Other histiocytic syndromes are described in Table 1: Histiocytic Syndromes: The Histiocytic Syndromes.

Table 1
The Histiocytic Syndromes Category Disorders Disorders of varied biologic behavior Dendritic cell-related Langerhans' cell histiocytosis (histiocytosis X) Eosinophilic granuloma Letterer-Siwe disease Hand-Schüller-Christian disease Other rare disorders Macrophage-related Hemophagocytic syndromes Primary hemophagocytic syndromes Familial Sporadic Secondary hemophagocytic syndromes Infection, malignancy, etc. Sinus histiocytosis with massive lymphadenopathy Other rare disorders Malignant disorders   Leukemias Acute monocytic and myelomonocytic leukemia Chronic myelomonocytic leukemia (CMML) Adult CMML Childhood JMML (juvenile myelomonocytic leukemia) Other rare disorders Adapted from Komp DM, Perry MC: “Introduction: The histiocytic syndromes.” Seminars in Oncology 18:1, 1991 and Favara BE, Feller AC, Pauli M, eds.: “Contemporary classification of histiocytic disorders.” Med Pediatr Oncol 29:157, 1997.

Last full review/revision November 2005

Content last modified November 2005