[An ophthalmologic diagnostic error leading to a rare systemic diagnosis: Erdheim-Chester disease]

Erdheim-Chester disease is a rare systemic disease. The diagnosis is difficult due to significant clinical and morphological polymorphism. Orbital involvement is rare, but constitutes a classic means of detection.

We report the case of a 60-year-old man, who consulted for evaluation of bilateral retro-orbital tumors. These tumors had been discovered on head CT two years previously during work-up of proptosis. Two biopsies were performed. The first one revealed polymorphous inflammatory tissue. The second one revealed intense granulomatous reaction, rich in non-specific foamy histiocytes. Thoracic-abdominal-pelvic CT scan detected peri-aortic and retroperitoneal infiltration. The association of these signs pointed to a diagnosis of Erdheim-Chester disease, confirmed by the re-examination of the histological samples.

Erdheim-Chester disease is a rare non-Langerhans histiocytosis with a specific tropism for perivascular and fatty connective tissue. The cause is not known. The diagnosis of this systemic disease is histological.

In the case of bilateral intra-orbital tumors, the diagnosis of Erdheim-Chester disease must be considered.