Benign Episodic Unilateral Mydriasis in a 52-Year-Old Female.

Benign episodic unilateral mydriasis (BEUM) is a very rare, under-recognized condition characterized by transient, self-limited episodes of unilateral pupil dilation. It may frequently be part of a migraine process and may present as a diagnostic challenge due to its potential to mimic more serious neurological or ophthalmological conditions. In this case report, we describe the case of a 52-year-old female with a medical history significant for hypertension, anxiety, prior right retinal detachment, and longstanding migraines, who presented with a new onset of recurrent, episodic left-sided mydriasis accompanied by ipsilateral headaches. This paper will outline the findings, medical thought processes, and different diagnoses considered when the patient was assessed in the emergency department and during her hospital stay.