Erdheim-Chester disease: a rare non-Langerhans histiocytosis.

A 3-year-old girl was admitted to our hospital with diabetes insipidus and a left eye proptosis. During investigation of diabetes insipidus, an extensive osteolytic mass, involving skull base and maxillo-facial bones, was revealed. Biopsy exhibited dense infiltrate of foamy histiocytes, which were positive for CD68 and CD163 and negative for CD1a and S100 confirming histopathological diagnosis of Erdheim-Chester disease. Treatment with dabrafenib was initiated, with good response and no side effects.