"Coated aorta": A new sign of Erdheim-Chester disease

Erdheim-Chester disease is a rare, non-langerhans cell form of histiocytosi s characterized by osteosclerosis of the metaphyseal regions of long bones, diabetes insipidus, proptosis, and retroperitoneal fibrosis. The latter us ually involves the perirenal area and leads to hydronephrosis. Periaortic f ibrosis is less frequent. We describe 3 unusual cases of Erdheim-Chester di sease with periaortic fibrosis involving the whole aorta and leading to a " coated aorta" appearance on computed tomography scans. Faced with such a si ngular "coated aorta," bone scintigraphy can be very helpful when searching for Erdheim-Chester disease.