Alternative Names
Autism-Dementia-Ataxia-Loss of Purposeful Hand Use Syndrome; Cerebroatrophic Hyperammonemia; Rett's Syndrome; RTS; RTT
Symptoms & Characteristics
Rett syndrome is a genetic condition that causes developmental and nervous system problems, characteristically affecting females. Infants with Rett syndrome seem to grow and develop normally at first. Then, sometime between 3 months old and 3 years old, affected children stop progressing in their development and even lose some skills. Common characteristics include:
- loss of hand movements (such as grasping)
- compulsive movements (such as hand wringing)
Some affected people live into middle age and beyond but need care throughout their lives.
Treatment
There is no cure for Rett syndrome. Early diagnosis, routine surveillance and treatment can help to manage some of the symptoms and sometimes prevent related problems.
How Common Is It?
About 1 in 10,000 to 1 in 22,000 people are affected with Rett syndrome.
Genetics & Inheritance
Rett syndrome is caused by mutations in a gene called MECP2 on the X chromosome at the location q28.
Females have two X chromosomes, and therefore have two copies of the MECP2 gene. Males have one X chromosome and one Y chromosome and therefore, have only one copy of the MECP2 gene. In Rett syndrome, having a mutation in a single gene copy is sufficient enough to cause the disease. However, as males do not have second gene to compensate, Rett syndrome is typically more severe (even lethal) in males. This is called X-linked dominant inheritance.
- About 99.5% of affected people are the first one in their family to be affected. Their mutation is a result of a sporadic, new ("de novo") mutation.
- An affected person has a 50% chance with each pregnancy to have an affected child.
Parents of an affected person may want to consider genetic testing for Rett syndrome themselves. The benefits and limitations of such testing should be discussed with a qualified health care professional.
- If both parents have negative genetic testing, recurrence risk to have another affected child may still be increased over the general population. This may be due to a complex concept called germline mosaicism in which some of a person's egg or sperm cells may have a disease causing mutation, while the rest of the cells in their body do not.
- Also, in rare cases, the mother of an affected person has been found to the same mutation but none of the physical features (or very mild features) of Rett syndrome. This is due to concept is called skewed X-inactivation. In females, if both X chromosomes are active, then all the genes on the X chromosome would be expressed at twice the rate in female cells compared to in male cells. To make sure both males and females have a comparable amount of expressed genes, in female cells, one X chromosome is randomly selected and inactivated, while the other one remains active. Sometimes, when one X chromosome has a damaged gene, that X is preferentially inactivated in all or most of the females' cells. It is in this way that a female may have Rett syndrome but not show symptoms (or show mild symptoms).
There are other genetic conditions that have characteristics that overlap with Rett syndrome. There are also variations of Rett syndrome. A genetic consultation with a trained genetic professional is important for a complete evaluation, accurate diagnosis, as well as discussion of the benefits and limitations of testing and recurrence risk.
Genetic Testing
Clinical genetic testing for Rett syndrome may be available through an in person genetic consultation for people who are considered at risk. Use our find a genetic professional directory to locate a trained genetic professional in your area.
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