[Difficult diagnosis of Erdheim Chester disease revealed by central diabetes insipidus]

The Erdheim Chester disease is a rare form of non Langerhans cell histiocytosis. Its rarity and its unspecific clinical presentation, make that its diagnosis is often delayed. We report the case of a 50 years old female who has an Erdheim Chester disease, revealed by a central diabetes insipidus with thickening of the pituitary stalk, with associated gonadotropin deficiency. The Erdheim Chester disease was suspected because of the association with other evocative systemic lesions: eyelid xanthelasmas and bone lesions in metaphyseal-diaphyseal region of the upper and lower ends of both femurs and tibias on bone scan. Confirmation of the diagnosis was initially difficult and delayed, with initially inconclusive cutaneous and bone biopsies. It is the histological re-reading with immunohistochemical study of the bone biopsies which allowed the diagnosis by showing histiocytes positive for the CD68 and negative for the CD1a and the protein S100. The diagnosis was made with a delay of 3 years. In conclusion, although rare, Erdheim Chester disease should be suspected in front of a set of clinical and radiological arguments. Diagnostic confirmation is based on histological and especially immunohistochemical studies.