Rett's Disorder is included as a Pervasive Developmental Disorder because there is some potential confusion with autism - particularly in the preschool years (Tsai,1992). Otherwise the course and onset of this condition is very distinctive.
In people with Rett's Disorder (first reported by Rett in 1966), very early development is normal. Head growth then decelerates, usually in the first months of life and a loss of purposeful hand movements occurs. Motor involvement is quite striking and profound mental retardation is typical. Characteristic hand-washing stereotypies develop.
While the DSM-IV does not list male sex in the exclusionary criteria, the existing literature on Rett's syndrome documents the condition primarily in girls. The DSM-IV field trial sample included only girls and a recent, very well executed epidemiological investigation documented a prevalence of 3.8 per 10,000 girls; boys were not included.Since the discovery of the MECP2 gene, responsible for Rett's, variants of the syndrome have been reported in males who have mutations of MECP2, with some overlap in the symptomatology observed in girls (Amir, Van de Veyver, Wan, Tran, Franke, & Zoghbi, 1999; Schwartzman, Zatz, Vasquez, Gomes, Koiffman, Fridman & Otto, 1999; Schanen, Kurczynski, Brunelle, Woodcock, Dure, & Percy 1998). A national network of parents has formed the Rett Syndrome Association.