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About Rett Syndrome

What is Rett Syndrome?

Rett syndrome is a severe neurological disorder that is diagnosed primarily in girls and begins to manifest itself during the toddler years. After a seemingly normal first year the child begins to lose previously acquired skills. This regression can happen quickly over a number of days or very gradually over months. Often the first noticeable symptoms include low muscle tone (hypotonia), eye crossing, decreased interactions with people and surroundings, and loss of hand function. The hallmark symptom of Rett is repetitive hand movements that can be constant, especially in younger children.

As time passes additional symptoms may include loss of speech, trouble with balance and motor coordination, irritability and crying, and disrupted sleep patterns. Many children develop seizures, anxiety, breathing problems, gastrointestinal and orthopedic issues, as well as oral motor difficulties.

It is important to note that Rett is a spectrum disorder, with children exhibiting a broad range of severity. Some children have some language, can run, and feed themselves while others are unable to independently sit up. The symptoms in Rett are, unfortunately, many and oftentimes debilitating. Our children, however, are so much more than their symptoms. They are beautiful, they are powerful, they are resilient. They move us to move mountains on their behalf.

Is There a Cure for Rett Syndrome?

Although there currently is no cure for people with Rett syndrome, the sole focus of the Rett Syndrome Research Trust is to identify a cure as quickly as possible. We are optimistic about a cure because Rett-like symptoms have been dramatically reversed in animal models of the disorder.

Curing the disorder will require targeting the root cause: mutations in the MECP2 gene. RSRT has identified six genetic-based strategies that address Rett’s underlying cause and is working aggressively to transition knowledge and resources to biopharmaceutical companies, which will further develop and commercialize a curative treatment.

To date there are eight companies pursuing genetic-based medicines for Rett syndrome. All of these programs leverage discoveries and resources that were incubated with RSRT funding.

How Many People Have Rett Syndrome?

It is estimated that one in 10,000 girls is born with Rett syndrome. This means about 15,000 girls and women in the US and 350,000 worldwide have the disorder. The incidence of Rett syndrome in males is currently unknown.

Rett syndrome is classified as a “rare disease” (by definition, less than 200,000 affected individuals in the US) by the Office of Rare Diseases of the National Institutes of Health. This designation qualifies the condition for orphan drug status from the FDA, which comes with certain perks for pharmaceutical companies, such as tax deductions and marketing exclusivity on a drug for an extended time period.


What Causes Rett Syndrome?

Rett is caused by errors in a gene called MECP2, which is located on the X chromosome. All of us have an MECP2 gene in every one of our cells that makes a protein also called MECP2. Children with Rett have a mutation in the gene that causes the protein to not work properly. The MECP2 protein is present throughout the body, but it is especially important in the brain, where it helps keep brain cells functioning properly.

To better understand your child’s mutation and what it means for her future please visit our Genetics Primer.

Why Do Mostly Girls Have Rett Syndrome?

Many studies have provided evidence that the vast majority of MECP2 mutations originate in the sperm. Since fathers give an X chromosome to their daughters and a Y chromosome to their sons, the MECP2 mutation in a sperm can only be transmitted from father to daughter. This is the reason why Rett is seen primarily in girls.

Due to the sheer volume of sperm that is continuously made it is likely that all men produce sperm with MECP2 mutations. One in about 20,000 eggs will be fertilized with a sperm that has an MECP2 mutation in it — the cruel reality of genetic roulette.

When boys have Rett their MECP2 mutation comes from their mother’s egg. Sometimes, however, the mutation can also originate in a single cell as the male embryo is developing. This is called somatic mosaicism.

Scientific papers over the years have hypothesized that because male fetuses have only one X chromosome their disease would be so severe that they might not develop to full term and the mothers might miscarry. However, there is no clinical data to support this hypothesis.

Learn More About Rett Syndrome Genetics

If you'd like to learn more about the genetics of Rett syndrome, read our Genetics Primer. It will take the mystery out of your child's genetics results and answer common questions, such as the correlation between mutations and symptoms, where did the mutation come from, who in your family should be tested, and more.


How Is Rett Syndrome Diagnosed?

Rett syndrome is a clinical diagnosis given by a physician based on the child’s history and symptoms. An MECP2 mutation is not required to have a clinical diagnosis of Rett syndrome. In other words, it is possible to have a diagnosis of Rett without genetic confirmation or the other way around — an individual can have an MECP2 mutation without a clinical diagnosis of Rett syndrome.

If your child’s symptoms are consistent with Rett syndrome but your child has tested negative for an MECP2 mutation, please ensure that testing included sequencing all four exons of MECP2 and that deletion testing was done as well (sometimes called MLPA). If you have questions about your child’s testing result, please contact us.

What Are Rett Syndrome's Symptoms and Health Problems?

An individual with Rett will have a variety of problems that may include movement issues (apraxia, rigidity, dyskinesia, dystonia, tremors), seizures, gastrointestinal problems (reflux, constipation), orthopedic issues (contractures, scoliosis, hip problems), autonomic issues (breathing irregularities, cardiac problems, swallowing), as well as sleep problems and anxiety.

Having compassionate doctors in place that will listen to you is key. In addition to a pediatrician you may need a neurologist, a gastroenterologist, and an orthopedist. It’s important to note that not every child will have every symptom, so the team of doctors required may vary.

Since most primary care doctors have limited experience with Rett syndrome, a consensus on guidelines about how to care for individuals with Rett syndrome was published in 2020. We hope this publication will be helpful to you, and we encourage you to share it with your child’s doctors.

What Are The Treatments For Rett Syndrome?

Many medications are often used to treat seizures, anxiety, reflux, constipation, sleep problems, movement issues, and more. Surgeries to insert feeding tubes or correct scoliosis or other orthopedic problems are not unusual.

Daybue/Trofinetide was recently approved by the FDA to treat Rett syndrome. Click here to access DAYBUE: Key facts for Parents.