Erdheim–Chester disease (ECD) is a rare non-Langherans histiocytosis associated with multiple organ systems. Typical features include osteosclerotic lesions in the metaphysis of long tubular bones, exophthalmia, pulmonary and retroperitoneal fibrosis,¹ which highlight the diagnostic difficulties that ECD presents. Intracranial association is exceptional and its treatment is controversial.²

We present the case of a 52-year-old man with a history of progressive visual deficit, pseudotumour cerebrums and diabetes insipidus, who presented …