Wyburn-Mason syndrome, also known as Bonnet- Dechaume-BIanc syndrome, is a rare condition that is characterized by arteriovenous malformations (i.e., abnormal communication between the arteries and veins) in the central nervous system and the retina. These malformations take the form of arteriovenous aneurysms, which are widenings of the walls of an artery and a vein with abnormal blood flow between the vessels. This condition is considered to be congenital, and it is passed on via autosomal dominant inheritance, which means that an affected person has a 50% chance of passing the trait to a child. In 1937, Bonnet et al. recognized the coexistence of retinal and cerebral arteriovenous malformations (AVMs). In 1943, Wyburn-Mason recorded cases of arteriovenous malformations of the midbrain, retina, and facial nevi and found that this syndrome may also be associated with mental changes in some cases.