Langerhans cell histiocytosis refers to a rare group of diseases that derive from a clonal proliferation and accumulation of Langerhans cells (1). The latter are specialized antigen-presenting cells of dendritic origin present at the dermal/epidermal border of the skin and as a meshwork throughout the epidermis. The Histiocyte Society, an international network of European, North and South American, and Asian groups that conduct cooperative studies of the histiocytoses, has divided histiocytic diseases into three groups: Langerhans cell histiocytosis (class I), non- Langerhans cell histiocytoses (class II), and malignant histiocytoses (class III) (2, 3). Langerhans cell histiocytosis, historically known as histiocytosis X, eosinophilic granuloma, or Langerhans cell granulomatosis, encompasses many different clinical manifestations. The Histiocyte Society classifies Langerhans cell histiocytosis according to the number of sites and types of tissue/organ involved and the presence or absence of involved organ failure. Historically, the disease comprises three main and sometimes overlapping clinical syndromes: unifocal disease (solitary eosinophilic granuloma), multifocal unisystem disease (including cases of Hand-Schüller-Christian syndrome), and multifocal multisystem disease (including cases of Letterer-Siwe syndrome) (1; 4–6). Langerhans cell histiocytosis also encompasses some cases belonging to syndromes previously described as reticuloendotheliosis, Hashimoto- Pritzker syndrome, self-healing histiocytosis, pure cutaneous histiocytosis, Type II histiocytosis, and nonlipid reticuloendotheliosis.
KeywordsDiabetes Insipidus Eosinophilic Granuloma Birbeck Granule Histiocyte Society Solitary Eosinophilic Granuloma
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