By Mary Catherine Meno
What is it?
Rett Syndrome (RTT) is a neurological disorder that causes impairments that impact every aspect of someone’s life. This includes their ability to eat, speak, walk, and/or breathe easily. The disorder is almost only found in girls and is a postnatal disorder, meaning that symptoms develop after the child is born, typically after 6 months of age (NCBI). The mutation that causes RTT is on a gene that controls the expressivity and functions of other genes. An individual’s inability to perform daily actions is caused by the mutated gene interfering with cell communication and protein production. Life expectancy for those with Rett Syndrome is shortened and most patients live into their 40s or 50s (“Rett Syndrome: Frequently [. . . ]”). During those years, there is often no improvement of the condition though individuals can participate in various types of therapy to lessen their symptoms and help them communicate. In most cases, the condition does not decline, however, meaning that after the first couple years the state of the affected individual will not worsen as they get older.
What’s the trait?
Rett Syndrome is caused by mutations on the MeCP2 gene that is found on the X chromosome, the reason it is found almost exclusively in females. The disorder affects about 1 in every 10,000 births, a very rare condition (NCBI). MeCP2 is a methylation protein, so in the DNA it turns off certain genes (i.e. muscles don’t need to produce neurons, etc.) but the mutation turns off genes that it’s not supposed to, a phenomenon called X-inactivation. The mutation is also linked to various other diseases including Angelman syndrome and lupus (MECP2).
Why get tested?
Genetic testing can be done with a simple blood test and is the primary way to confirm diagnosis for Rett Syndrome. The primary gene involved with RTT is the MeCP2 gene that essentially is in charge of turning on and off certain genes based on their function and the area that they are contained in. With the results families are also able to learn about the specific mutation that their child has. There are many clinical trials taking place and testing positive for RTT is one step towards being eligible for these trials. By obtaining test results, the information can also be used, with permission, to increase the current knowledge of Rett Syndrome and MeCP2 mutations (“Rett Syndrome Diagnosis”). The most cost-effective test would be a single DNA gene sequencing test, as there is only one gene currently known to be associated with RTT. This test ranges from $100-$300. A test that confirms a mutation in MeCP2 does not necessarily confirm Rett Syndrome, as mutations on the gene are also associated with other disorders. Results showing a mutation on the MeCP2 gene indicates a small range of disorders and determining which mutation the individual has as well as a doctor’s diagnosis of the symptoms will be able to tell you and your family if your child has RTT (MECP2). The majority of RTT cases are caused by a mutation on MeCP2, however there are a few situations where this was not the case. Therefore, if the results are negative there are is a small chance your child could still be affected, but this is largely depended on the symptoms they are showing and the doctor’s analysis.
Think Before You Spit
While there are certainly benefits to getting tested, there are potential downsides as well. As mentioned above, 80-97% of cases are caused by mutations in the MeCP2 gene but there is a small chance that the results could be negative and the individual still be affected. It should also be considered before ordering testing that this disorder is not inherited. Understanding a family member’s gene sequence would not provide any information as to whether or not the child is likely to be affected as less than 1% of cases are inherited from parents, and having one child with Rett Syndrome does not increase the chances of having a second child with the disorder (“Rett Syndrome: Testing [. . . ]”).
Ethical Considerations
When ordering a DNA test for Rett Syndrome, it is likely going to be from doctor’s orders rather than an at home test. This means that the results will be less commercialized and that the privacy around the results will be higher. Single gene sequencing cost is not as high as other testing options but could still be a burden on families, as well as the post-results resources needed for helping with care. The emotional burden of finding out the results will likely be lower than being tested blindly. Getting tested means that you are confirming a doctor’s diagnosis, so families will have already received the news. A positive result would most likely be the best outcome, because it is confirming previous suspicions. A negative result could lead to further testing to understand what is causing the child’s symptoms and potential confusion before finding a diagnosis.
Asking the Right Questions
Most people understand that their genes can be passed down to their children, but it is important to understand that Rett Syndrome is not passed down through genetics. It’s a rare mutation that occurs sporadically, so a child testing positive for RTT does not increase any family member’s chances of having the mutation. While it is possible for someone to be an asymptomatic carrier, this happens in less than 1% of cases and prenatal screening can be completed in these situations (“Rett Syndrome Fact [. . . ]”). Families should be prepared to explore further testing options if the results are negative, as it would be necessary for diagnosis. Testing for Rett Syndrome without doctor recommendations is not suggested, as the test is gene specific and the disorder is very rare. However, if someone does get tested and the results are positive, it is highly recommended to share these results with the doctor in order to become more knowledgeable about resources and support.
All evidence points to getting tested if diagnosed by a doctor, as it is the only way to confirm the diagnosis. Individuals are also eligible for clinical trials if they test positive, and there are no clinical downsides to getting tested. One study pushes people to get tested if diagnosed because once the mutation is confirmed, researchers can look at the early childhood of the individual to help understand “the early phenotype of RTT” (Marschik, et al). There are a multitude of studies working to explore and understand Rett Syndrome, but there are almost no studies on the negative side of being tested.
Sources
Huldie, Janine. “Rett Syndrome Awareness for One and All… – Janine’s Confessions of a Mommyaholic.” This Mom’s Confessions, 19 Dec. 2016, www.janinehuldie.com/1051/.
Marschik, Peter B, et al. “Early Development in Rett Syndrome – the Benefits and Difficulties of a Birth Cohort Approach.” Developmental Neurorehabilitation, Taylor & Francis, Jan. 2018, www.ncbi.nlm.nih.gov/pmc/articles/PMC5796587/.
“MECP2.” SNPedia, 6 Oct. 2015, www.snpedia.com/index.php/MECP2.
National Center for Biotechnology Information (US). “Rett Syndrome.” Genes and Disease [Internet]., U.S. National Library of Medicine, 1 Jan. 1998, www.ncbi.nlm.nih.gov/books/NBK22188/.
“Rett Syndrome Diagnosis.” Rettsyndrome.org, www.rettsyndrome.org/about-rett-syndrome/rett-syndrome-diagnosis/.
“Rett Syndrome Fact Sheet.” National Institute of Neurological Disorders and Stroke, U.S. Department of Health and Human Services, 13 Aug. 2019, www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Rett-Syndrome-Fact-Sheet.
“Rett Syndrome: Frequently Asked Questions: Boston Children’s Hospital.” Boston Children’s Hospital, www.childrenshospital.org/conditions-and-treatments/conditions/r/rett-syndrome/frequently-asked-questions.
“Rett Syndrome: Testing and Diagnosis: Boston Children’s Hospital.” Boston Children’s Hospital, www.childrenshospital.org/conditions-and-treatments/conditions/r/rett-syndrome/testing-and-diagnosis.