Langerhansian histiocytosis (LH) is a group of disorders characterized by tissue infiltration by Langerhans cells or dendritic cells originating from the reticuloendothelial system and organized in granulomas. The Langerhansian nature of the disease is confirmed by immunohistochemistry, with expression of CD1a or langerin/CD207, or by electron microscopy, with the presence of Birbeck granules [1,2].It is a rare disease that mainly affects children and young adults [1].It encompasses a range of entities with widely varying clinical presentation and prognosis, from a simple eosinophilic granuloma to a multivisceral form with organ dysfunction, and has led to a number of different names [1,3]: "Abt- Letterer-Siwe disease", the rapidly progressing acute form; "Hand-Schuller-Christian syndrome", the chronic form; "eosinophilic granuloma", the circumscribed form; and Hashimoto-Pritzker disease, a spontaneously regressing form [4].Although progress has been made in understanding the pathogenesis of the disease, its etiology remains unknown [3].