Wyburn Mason's syndrome is a condition in which blood vessels do not form correctly in both the retina of one eye and a part of the brain. These malformed blood vessels are called arteriovenous malformations (AVM). Wyburn Mason's syndrome is present from birth (congenital) and the cause is unknown. Individuals with this condition may have additional AVMs in other parts of the body, particularly the face. The symptoms of this condition are quite variable and depend on the size, location, and shape of the AVMs. Affected individuals may have no symptoms or may experience headaches, problems with vision, seizures, or partial paralysis (hemiparesis).