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7. What is Rett syndrome?

Rett syndrome is a disorder of the nervous system that has some of the same  characteristics as autism. Both diseases strike at an early age, and a loss of language and social interaction are common in both.

Like autism, children suffering from Rett syndrome will avoid eye contact, have a diminished ability to express feelings, and will exhibit purposeless hand movements such as flapping, wringing, or waving. Seizures are common in both diseases, and neither has a known cure.

Despite the similarities, Rett syndrome and autism are distinct diseases with many differences that distinguish them. Autism is a disease with a male predominance, while Rett syndrome is found in females almost exclusively.

The neurologic deficits of autism remain stable; however, Rett syndrome is a progressive neurological disorder, whose symptoms worsen as the child gets older. Autistic children are often first diagnosed because of speech and social interaction, though the first symptom noticed in children with Rett syndrome is loss of muscle tone (called hypotonia by physicians.)

Like autism, Rett syndrome knows no geographic, racial, or social boundaries. Fewer then 1 percent of Rett cases have a familial inheritance pattern; that is, very few cases are found in families who have relatives with Rett syndrome.

Rett syndrome is known to be associated with mutations in the gene MECP2 located on the X chromosome. It is not known if this gene mutation causes Rett syndrome or is just a marker for the disease. Nevertheless, the discovery of the MECP2 gene has made possible the development of a blood test for Rett syndrome. Approximately 85 percent of all patients diagnosed with Rett syndrome also test positive for an MECP2 mutation.

This does not mean that the remaining 15 percent do not have Rett syndrome. Although testing positive for a mutation confirms the diagnosis, it is not required. The diagnosis of the disorder, however, is still based on symptoms and clinical history. It is possible that mutations exist in an area of MECP2 that has not yet been sequenced or perhaps other genes contribute to Rett syndrome. No blood test yet exists for the diagnosis of autism.

The following criteria are used for making a clinical diagnosis of Rett syndrome. Please keep in mind that Rett syndrome is a spectrum disorder like autism. Not all the symptoms are seen in every patient and the severity of a symptom may vary widely from patient to patient.

Diagnostic Criteria

  • Period of apparent normal development until 6–18 months
  • Regression (in other words, a change from normal early development into impaired abilities)
  • Diminished ability to express feelings
  • Avoidance of eye contact
  • Grinding teeth
  • Loss of verbal language
  • Purposeful hand use replaced by stereotypical hand movements such as flapping or waving
  • Normal head circumference at birth followed by slowing of the rate of head growth
  • If able to walk, gait is usually wide-based and stiff-legged
  • Shakiness of torso and/or limbs, especially when upset
  • Growth retardation and decreased body fat and muscle mass

Although some individuals with Rett syndrome die at a young age, the majority live into adulthood. Autism, on the other hand, is not associated with a reduced life span.

Terms:

Hypotonia - Decreased muscle tone.

Gene - Originally defined as the physical unit of heredity, it is probably best defined as the unit of inheritance that occupies a specific locus on a chromosome, the existence of which can be confirmed by the occurrence of different allelic forms.

Genes are formed from DNA, carried on the chromosomes, and are responsible for the inherited characteristics that distinguish one individual from another. Each human individual has an estimated 100,000 separate genes.

Chromosome Structure in the cell nucleus that bears an individual’s genetic information.

 

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