A Rare Case in the Emergency Department: Holmes-Adie Syndrome.

Holmes-Adie syndrome (HAS) is a rare syndrome characterized by tonic pupil and the absence of deep tendon reflexes. HAS was first described in 1931 and is usually idiopathic, with incidences reported to be 4-7 per 100,000. Although tonic pupil is usually unilateral, it can also be bilateral. Enlarged and irregular pupil is usually noticed by the patient. Light reflex is weak or unresponsive. Another characteristic of HAS is the absence of deep tendon reflexes, and unilateral involvement is more common. This case report emphasizes that HAS should be considered in the differential diagnosis of patients presenting to the emergency department with anisocoria, and the dilute pilocarpine test can be used in diagnosis.