In around 99% of cases Rett syndrome is caused by a change in the DNA (referred to as a mutation) of the gene named MECP2 which is found on the X chromosome. This gene contains the instructions for the body to make a protein that is vital for brain development. The gene mutation prevents nerve cells in the brain from functioning normally. Read more about Rett syndrome.
How is Rett syndrome diagnosed?
Doctors can clinically diagnose Rett syndrome by observing signs and symptoms during the child's early growth and development, and conducting ongoing evaluations of the child's physical and neurological status. There is also now a genetic test to complement the clinical diagnosis, which involves searching for the MECP2 mutation on the child's X chromosome. Read more about the diagnosis and the diagnostic criteria used here.
As it is genetic in origin, is it hereditary?
The mutation in the gene is almost exclusively a new mutation (sometimes referred to as a De Novo mutation) occuring in that child and the parents are not carriers of a mutated gene. In a very small number of cases, more than one child with Rett syndrome has been born to the same parents. Where this occurs geneticists have found that there are female family members who have a mutation of their MECP2 gene but do not show clinical symptoms. These females are known as “asymptomatic female carriers. However, the risk of having a second child with the disorder is less than one percent.
Why are so few boys affected?
The problem sits on an X Chromosome of which girls have two. Boys have only one X chromosome (and one Y chromosome) so they lack a back-up copy that could compensate for the defective one.
If a boy carries a similar MECP2 mutation (to those found in females with Rett syndrome) on his single X chromosome, with no other ‘normal’ X chromosome to compensate, then he will usually be affected much more severely even than a female.
Sometimes a boy will be born with a MECP2 alteration, usually found in those with classic RTT, but where it often has a less severe effect than some of the other gene alterations.
For the clinical features of Rett syndrome to develop in a boy, the mutation should usually be present and expressed in just some of his cells – as happens in a female.
The incidence of Rett syndrome in boys is believed to be around 1:40,000.
Are some people Rett syndrome more severely affected than others?
Yes there is a range of severity of symptoms. The severity of the symptoms will vary depending upon the percentage of their cells that express a normal copy of the MECP2 gene. If the active X chromosome that is carrying the defective gene is turned off in a large proportion of cells, the symptoms will be mild, but if a larger percentage of cells have the X chromosome with the normal MECP2 gene turned off, onset of the disorder may occur earlier and the symptoms may be more severe. Clinicians and researchers have also seen variances in the severity of the disorder depending on the type of mutation and where the mutation occurs on the X Chromosome. Sometimes this is referred to as the genotype/phenotype (the correlation between the gene mutation and the behaviour). More information of the different mutations is available in this paper The association between behaviour and genotype in Rett Syndrome using the Australian Rett Syndrome Database.
Can Rett syndrome be cured?
There is currently no cure for Rett syndrome and treatment for the disorder is focused on the management of symptoms, requiring a multidisciplinary approach. However, in 2007, Dr Adrian Bird at the University of Edinburgh showed that Rett syndrome was reversible in laboratory mice. Read more about this here. It is possible that Rett syndrome could be the world's first curable neurological disorder and could also provide the key in helping with disorders such as Alzheimer’s, Autism, Bipolar Disorder, Parkinsons and Schizophrenia. But clearly mice are very different to humans and much still needs to be done to progress this work into something that is safe and effective for people with Rett syndrome to use.
How can Rett UK help?
Rett UK has over 30 years experience of supporting families affected by the disorder. We are in a unique position of holding a wealth of information gained from the families of those children first diagnosed in the UK and are supported by our key medical advisers, including Dr Hilary Cass and Dr Angus Clarke, who are extremely experienced in Rett syndrome.
Rett UK has a national helpline, 01582 798911, operated by our Family Support Team who are professionally trained, very knowledgeable in Rett syndrome as well as having solid personal and practical experience supporting people with disabilities in various settings. We also hold specialist NHS led Rett Clinics at four centres around the UK, have Regional Events, a Family Weekend, local support groups and a parent to parent contact network. Find out more about our support services here.
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Thursday, 19 April, 2018
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