description of rett syndrome
Rett syndrome is a neurological disorder found almost exclusively in females. Infants and children with the disorder usually develop normally until approximately age 6 to 18 months. They then cease to acquire new skills and gradually or suddenly lose previously acquired abilities, such as conscious control of the hands and the ability to vocalize most sounds or words.
It has a prevalence of approximately 1 in 10 000 to 1 in 15 000 females between the ages of 5 and 18 years. There are about 200 girls in Australia who have been diagnosed with this condition.
Rett syndrome is a genetic disorder – it is caused by a mutation of the MECP2 gene, which is found on the X chromosome – but less than one percent of recorded cases are inherited. Most cases are sporadic – the mutation occurs randomly.
It was originally described by Dr. Andreas Rett of Austria in 1966, but did not become well known until twenty years later following publication of a report describing 35 affected girls from Sweden, Portugal, and France.
In the early onset stage – usually beginning between 6 and 18 months – there is only a subtle slowing of development, which may go unnoticed. Delays in gross motor skills such as sitting and crawling occur, and the child may make less eye contact and show less interest in toys. This stage may last from a few months to over a year.
At the rapid destructive stage – usually beginning between ages 1 and 4 and lasting for weeks or months – purposeful hand skills and spoken language abilities are lost. Characteristic hand movements, including repeated hand clapping, mouthing, tapping, washing, and/or wringing emerge. Breathing irregularities such as hyperventilation may occur. Some girls display autistic like symptoms such as loss of social interaction. Gait patterns (in those who have learned to walk) are unsteady and slowing of head growth is usually noticeable during this stage.
The plateau stage – usually beginning between ages 2 and 10 – may last for years. In this stage there is a relative stability of symptoms and there may be an improvement in behaviour, with less irritability, crying and autistic like features. However, motor difficulties and seizure activity may become more pronounced. Many females with the condition may remain for the rest of their lives in this stage of stabilization.
The late motor deterioration stage is characterised by reduced mobility and may last for years or decades. Some girls who have learned to walk may gradually lose this ability. Other difficulties may include increasing muscle weakness, spasticity, and joint contractures. Sustained muscle contractions may cause involuntary, potentially painful, twisting or distorted posturing of affected muscles (dystonia). Further abnormalities may include irregular, rapid, jerky movements, particularly of the forearms and lower legs. Scoliosis (curvature of the spine), particularly for those who are unable to walk, may become progressively severe during this stage. Eye contact and attention span however may improve and repetitive hand movements may decrease.