[Rett syndrome. A frequent cause of progressive mental retardation in girls].

We report 6 cases of Rett syndrome, a disorder that occurs only in girls and is characterized by slowly progressive deterioration of higher brain function, with dementia and autistic behavior, loss of purposeful use of the hands and deceleration of head growth. We consider interesting this report because Rett syndrome would be an important cause of mental retardation in girls, which has been overlooked until few years ago.