Erdheim-Chester Disease Presenting as Optic Neuritis: A Case Report and Review of the Literature.

We report a case of Erdheim-Chester disease in a patient who presented to the ophthalmology clinic with unilateral vision loss, optic disc swelling, and cluster-type headaches. Erdheim-Chester disease is a rare form of non-Langerhans cell histiocytosis characterized by a xanthogranulomatous process with multisystem organ involvement. The condition can be fatal due to renal or cardiovascular complications. Diagnosis is challenging due to the highly variable presentations and rarity of the disease, as demonstrated in this case. Our patient did not have systemic involvement and tested negative for the BRAFV600 mutation. As the findings are atypical and uncommon, clinicians should be aware of the ophthalmic manifestations and imaging features of this rare disease to establish an early diagnosis.