Rett syndrome is a neurodevelopmental disorder occuring almost exclusively in females and which begins in childhood. It consists of a loss of purposeful use of the hands, distinctive hand movements, slowed brain and head growth, gait abnormalities, seizures, and mental retardation. It is unusual in that the child first displays normal early development, but then progressively loses abilities.
Dr. Andreas Rett, an Austrian physician, first identified this condition in 1966 by publishing an article in a journal.
The first symptom after normal development is usually hypotonia, which is loss of muscle tone. Loss in manual dexterity and speech can then follow, as well as problems crawling or walking and diminished eye contact. Sudden onset of symptoms, including compulsive hand movements, can occur.
Rett syndrome generally begins between the ages of 6 and 18 months.
Genetic vulnerability
Rett syndrome has been associated with mutations in the MECP2 (meck-pea-two) gene, which is found on the X chromosome. Girls have another X chromosome that enables them to survive this defect; boys do not, instead having a Y chromosome, which probably explains why so few boys survive with this defect in the X chromosome.
About 75% of girls having Rett syndrome also have this MECP2 genetic mutation, and the genetic test is highly useful to confirm or suggest a clinical diagnosis. Improvements in genetic testing may increase the observed correlation between the mutation and the syndrome.
Occurrence
One in every 10,000 to 15,000 females suffers from Rett syndrome. But the disorder occurs spontaneously in most affected individuals rather than being inherited; the risk of a family having a first child with Rett syndrome then giving birth to a second child with the same problem is less than 1 percent.