[Erdheim-Chester disease : a differential diagnosis of retroperitoneal fibrosis]

Erdheim-Chester disease is a rare multisystemic non-Langerhans histiocytosis with about 500 reported cases. Typical features include retroperitoneal and perirenal fibrosis (hairy kidney), periaortitis with a coated aorta, osteosclerosis of the lower limbs, and sometimes exophthalmia or diabetes insipidus. Histology is the cornerstone for diagnosis showing an infiltrate with foamy histiocytes and occasional multinucleated giant cells (Touton cells). There is no standard treatment regimen, current options include corticosteroids, interferon alpha, systemic chemotherapy, and radiation therapy ; however, a better understanding of the pathophysiological mechanisms has allowed the emergence of novel targeted treatments such as vemurafenib, imatinib, and anakinra.