To describe a case of Wyburn-Mason Syndrome, which is a rare phakomatosis, and its associated optical coherence tomography findings.

A 5-year-old boy was referred to our clinic for decreased vision in his right eye. He had nevus flammeus on his right forehead, upper eyelid, and cheek. His best corrected visual acuity was hand motion in the right eye, in which a relative afferent pupillary defect was noted. Fundus examination of the right eye showed marked dilation and tortuosity of retinal vessels, which could not be discriminated between arteries and veins on the posterior pole. Optical coherence tomography showed multiple large intraretinal vessels without involvement of the internal limiting membrane. Cerebral angiography revealed arteriovenous malformations (AVMs) and feeder vessels from the internal carotid artery to the ophthalmic artery, extending to the ethmoidal artery in the nasal cavity.

Wyburn-Mason syndrome is a rare phakomatoses and shows unique retinal AVM. Misdiagnosis or undertreatment of Wyburn-Mason syndrome can lead to serious complications. Patients with facial nevus flammeus should undergo thorough ocular examinations to rule out this disorder. Optical coherence tomography is a useful method for understanding structural features of retinal vascular malformations in Wyburn-Mason syndrome.