Rett syndrome is a progressive neurodevelopmental condition that affects females almost exclusively. It is caused by a mutation in the MECP2 gene situated on the X-chromosome. This gene carries the information necessary to make the methyl-CpG-binding protein 2 or MeCP2. A healthy MeCP2 helps to maintain communication between nerve cells and regulates the activity of several genes in the brain. Mutations in the MECP2 gene can result in a decreased production of the protein, or production of dysfunctional protein, which affects the relay of messages from the brain to the rest of the body.

The characteristic clinical symptoms associated with Rett syndrome include problems in learning and coordination, language and communication issues, and seizures.

Genetic testing is performed to detect MECP2 gene mutations and can be used to confirm the diagnosis made based on clinical symptoms, and the medical and developmental history of the patient. It also can be used as a screening tool.  A simple blood test is used for genetic testing and no hospital stay is required.

Genetic testing for diagnosis

Once the physician suspects Rett syndrome based on the patient’s medical history and clinical symptoms, genetic testing will be performed to detect any genetic changes in the MECP2 gene to confirm the diagnosis.

About 80-97% of people with a clinical diagnosis of Rett syndrome have a disease-causing change in the MECP2 gene. Some cases of atypical Rett syndrome also may be caused by mutations in other genes such as the CDKL5NTNG1, and FOXG1 and a genetic test also can be used to detect these mutations.

Screening with genetic testing

The genetic mutation that causes Rett syndrome is rarely inherited. Instead, in the majority of reported cases, change in the MECP2 gene occurs de novo, i.e., the mutation is triggered spontaneously in the fetus. MECP2 mutation screening can be performed as part of newborn screening as early detection can help with close monitoring and early treatment initiation.

About 1% of Rett syndrome cases are caused by a mutation inherited from the parents; some female relatives of an individual affected by Rett syndrome may not show any clinical symptoms even if they have the MECP2 mutation. Such female members are called asymptomatic, or silent carriers. Therefore, once Rett syndrome diagnosis has been confirmed in an individual, it is recommended that family members also be screened for the mutation.

Testing is more relevant in women because men with Rett syndrome have severe problems and very rarely go undiagnosed.

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