Erdheim-Chester disease is a rare form of systemic non-Langerhans cell histiocytosis characterized by infiltration by lipid-laden or foamy histiocytes. Osseous involvement, major diagnostic criteria, is constant and characteristic. It presents as metaphyseal and diaphyseal osteosclerosis, mainly affecting the long bones of the lower limbs. A few cases with axial skeleton involvement have been reported. Extra-osseous lesions may affect the retroperitoneum, lungs, skin, heart, brain and orbits. Prognosis depends mainly on the extra-osseous disease, mainly heart and lung involvement. Diagnosis is based on the combination of radiographic features, nuclear medicine features and nearly pathognomonic immunohistochemical profile. (C) 2011 Elsevier Masson SAS and Editions francaises de radiologie. All rights reserved.
