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Orbital Langerhans Cell Histiocytosis

Langerhans cell histiocytosis (LCH) is a rare disease with a long, confusing history. Formerly known as histiocytosis X, it is characterized by proliferation of cells with Langerhans cell (LC) characteristics. Annual incidence has been reported to be 3 to 7 cases per million people and its contribution to orbital disease in the general population is less than 1% of orbital tumors. LCH is a predominantly pediatric condition with a male predominance. Although our knowledge of LCH expanded significantly over the past century, the pathogenesis remains enigmatic, and natural history and treatment of orbital LCH are not well defined due to its extreme rarity.