Monozygotic twins discordant for Dandy-Walker malformation.

Dandy-Walker malformation is a congenital brain abnormality involving the fourth ventricle and cerebellum. We report on a case of twins discordant for this disorder diagnosed in the second trimester of gestation. The twin pregnancy was revealed to be monozygotic using DNA investigation. To our knowledge, this is the first time monozygotic twins discordant for Dandy-Walker malformation have been described.