[Erdheim-Chester disease and Langerhans histiocytosis. A fortuitous association?].

Erdheim-Chester disease is an idiopathic systemic histiocytosis hystologically different to Langerhans histiocytosis which is characterized by symmetric sclerotic bone lesions, predominantly affecting the diaphyseal and metaphyseal areas of large bones. It is not classified within malignant histiocytosis, but the clinical course tends to be aggressive with a poor response to different schedules of treatment. In rare cases the association of both entities has been reported: Erdheim-Chester disease and Langerhans histiocytosis. We present a new case with histological data of both histiocytosis whose clinical course included bone and muscle pain, insipidus diabetes, exophthalmos, bilateral symmetrical sclerosing bone lesions and a cerebellar syndrome.