Rett syndrome. A commonly overlooked progressive encephalopathy in girls.

We report 15 cases of Rett syndrome, a slowly progressive disorder that occurs only in girls and is characterized by early deterioration of higher brain function with dementia and autistic behavior, loss of purposeful use of the hands, and deceleration of head growth. Epilepsy, with minor motor seizures being the predominant type, has its onset between 2 and 4 years of age in the majority of cases. Additional features include an extrapyramidal disorder with dystonia and choreoathetosis, and lactic acidemia. A precise biochemical marker of this disorder has not been identified.