Erdheim-Chester disease: two cases of orbital involvement.

Erdheim-Chester disease (ECD) is an increasingly recognised form of fibro-inflammatory process characterised by xanthomatous histiocytes containing large amounts of ingested lipid, plasma cells, macrophages and Touton-type giant cells. Ophthalmic involvement in ECD has been reported in only 22 cases. We describe two patients, one presenting with diabetes insipidus and subsequently developing orbital pseudotumours and retroperitoneal fibrosis, the other presenting with exophthalmos and diplopia. The first patient was treated with cladribine and subsequently developed sudden onset of bilateral blindness while the second required radiation therapy for the retro-orbital process and developed radiation retinopathy. These cases typify the variable presentation and course in patients with ECD.