Rett syndrome is a rare neurodevelopmental disorder that almost exclusively affects girls. It is estimated to occur in one out of 10,000 to 23,000 female births.

The condition affects brain function and results in cognitive, emotional, sensory, motor, and autonomic problems. (Autonomic functions include heartbeat, breathing, and digestion).

Causes

Most Rett syndrome cases are caused by a mutation in the MECP2 gene, which is located on the X-chromosome. Because women have two X-chromosomes, they still have one functional copy of the MECP2 gene even if the other copy is mutated. Because males have only one X-chromosome, if they have a mutation in the MECP2 gene, they usually do not survive. However, very rarely Rett syndrome may occur in boys, but the disease appears earlier and is more severe than in girls with the same mutation.

More than 200 mutations in this gene have been identified. The location of the mutation within the gene and the type of mutation determine the course and severity of the disease.

The MECP2 gene provides instructions to build the so-called methyl-CpG binding protein 2 (MECP2). This protein regulates the activity of other genes — it can switch them on or off — and plays a critical role in brain development and function.

In most cases, mutations in the MECP2 gene occur spontaneously, although very rarely (in less than 1 percent of cases) Rett syndrome can be inherited.

Symptoms

Girls with Rett syndrome do not show any symptoms at birth, and the first symptoms usually appear between ages 6 to 18 months. They are subtle at first and may be overlooked. They include delays in gross motor skills such as crawling or sitting and reduced eye contact.

Between ages, 1 and 4, a decline in speaking and purposeful hand skills are observed. Stereotypic hand movements and breathing irregularities also may occur at this stage. Slowed head growth is another apparent symptom of Rett syndrome.

The disease usually reaches a plateau between ages, 2 and 10. This phase usually lasts for several years.

The last stage of the disease is characterized by muscle weakness, an abnormal curvature of the spine (scoliosis), and reduced mobility.

Diagnosis

Apart from the MECP2 gene, mutations in the CDKL5 or FOXG1 gene also have been linked to Rett syndrome, but these cause atypical types of the disease.

The disease can be diagnosed using a genetic test but because MECP2 mutations are not exclusive for Rett syndrome, clinical diagnostic criteria also are used. These include:

  • Impairment of acquired speaking skills
  • Impairment of acquired purposeful hand skills
  • Stereotypic hand movements
  • Gait abnormalities

Treatment

There is currently no cure for Rett syndrome, and treatments focus on symptom relief. For example, there are medications that can help improve breathing, sleep, and motor difficulties, as well as control seizures.

Splints and braces can help with scoliosis and may improve motor skills.

Occupational therapy can help develop the skills needed for daily activities.

Physiotherapy may improve mobility and walking abilities.

Speech and language therapy may help improve speaking problems or teach patients nonverbal ways of communication.

Research

There are multiple approaches being investigated to cure or change the course of Rett syndrome.

One approach is gene therapy, which aims to replace the defective copy of the MECP2 gene.

Another strategy is to activate the healthy copy of the MECP2 gene situated on the other X-chromosome.

Another method is to deliver the missing MECP2 protein to the body.

Finally, ways to “repair” the faulty MECP2 mRNA are being investigated. mRNA is a molecule that serves as an intermediate between DNA and protein. It contains the same genetic information as DNA, and is used as a template by the cell to make the corresponding protein.

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