Rett syndrome (RS) is a rare genetic disorder affecting mainly females (about one in 10,000 girls). And, boys who are stricken mostly die in infancy.
It is considered the second most frequent cause for severe and complex neurological dysfunction in females after Down syndrome. Patients with Rett syndrome are characterized by an array of neurological and orthopedic difficulties that mandate an intensive therapeutic intervention program for the duration of the individual's life.  In the majority of cases, it is caused by a mutation in MECP2, an X-linked gene, and considered the most common multi-disabling genetic disorder in females after Down syndrome.  However, MeCP2 dysfunction has also been shown to cause abnormalities of RNA splicing, suggesting a complex molecular pathogenesis. 
Individuals with Rett syndrome (RS) present a vast array of orthopedic and neurological difficulties. Typical problems, which may need to be addressed, when treating this population are functional limitations, low cardiovascular capacity, hypotonia, ataxia, apraxia, loss of transitional movements, spasticity, scoliosis and/or kyphosis, loss of ambulation, loss of hand function, foot deformities, and spatial disorientation. Lotan M from Chaim Sheba Medical Center , Israel, believes that an informed and intensely applied physical therapy regime can help the child and the family cope and even overcome the certain limitations. 
Recently, Dr. Adrian Bird, from Scotland's Edinburgh University found that gene therapy might be beneficial for Rett syndrome in his animal study. He first switched off MECP2 in male mice by inserting a chemical roadblock into the gene that they could switch on and off with medication. When the gene was switched off, baby mice hardly moved and died within weeks.
When he switched the gene back on gradually increasing gene activity, he rescued almost all mouse. Unfortunately, he couldn't test the cognitive functions but only the physical ones.
ALL RIGHTS RESERVED ZHION  Lotan M, Ben-Zeev B. Rett syndrome. A review with emphasis on clinical characteristics and intervention. ScientificWorldJournal. 2006 Dec 6;6:1517-41.  Lotan M. Rett syndrome. Guidelines for individual intervention. ScientificWorldJournal. 2006 Dec 6;6:1504-16.  Lotan M, Hanks S. Physical therapy intervention for individuals with Rett syndrome. ScientificWorldJournal. 2006 Oct 10;6:1314-38.  Moretti P, Zoghbi HY. MeCP2 dysfunction in Rett syndrome and related disorders. Curr Opin Genet Dev. 2006 Jun;16(3):276-81. Epub 2006 May 2.  Study raises hope for Rett syndrome cure AP February 2007