Erdheim-Chester Disease Presenting as Bilateral Facial Masses: A case report and review of literature.

Erdheim-Chester disease (ECD) is a rare form of non-Langerhans cell histiocytosis with unknown aetiology. It is recently recognised to be neoplastic with genetic mutations affecting the mitogen-activating protein kinase pathway. We report a 49-year-old female patient who initially presented in 2012 to a tertiary care centre in Muscat, Oman, with bilateral facial masses. These were removed but later recurred over a period of 10 years. She then presented with xanthelasmas, bone lesions, secondary infertility due to hypothalamic hypogonadism, diabetes insipidus and Hashimoto's hypothyroidism. The facial masses were biopsied and they showed classic morphological features in the form of diffuse infiltration by foamy histiocytes with scattered Touton type of giant cells, patchy lymphocytic infiltrates and dense fibrosis. The patient is stable and is being followed-up. The presented ECD case is particularly interesting due to the recurrent bilateral facial masses. To the best of the authors' knowledge, this is the first documented case in Oman.