Langerhans cell histiocytosis (LCH) is a rare disorder of the mononuclear-phagocyte system, capable of producing a broad spectrum of clinical disease from a self-limiting focal skeletal lesion to a fulminant, sometimes fatal, multisystem disorder. The association of LCH with central nervous system (CNS) disease dates back to the initial description by Hand in 1893 of a 3-year-old patient who presented with exophthalmos, polyuria, and localized osteomalacia of the skull. Hand initially attributed the constellation of findings to tuberculosis, although he later suggested the disease likely had a different cause [19]. The unknown etiology of this disease led to the proliferation of names for the various clinical presentations, including eosino-philic granuloma (EG) for localized skeletal lesions, Hand—Schuller—Christian disease for multifocal skull lesions and diabetes insipidus, and Abt—Letterer—Siwe disease for the disseminated form with multiple organ involvement. Lichenstein was the first to recognize the similarities that these clinical and pathological entities contained were due to one disease and coined the term histiocytosis X to encompass these histiocytic disorders of unknown etiology [24]. It was not until Nezelof, in 1973, described the resemblance between the ultrastructural elements of the normal Langerhans cell and those abnormal cells in histiocytosis X that the common cell of origin was discovered [21]. As a consequence of that discovery, “Langerhans cell histiocytosis” was proposed to replace “histiocytosis X” and to unify the varied clinicopathological entities [3].