Rett syndrome
Key points
- Rett syndrome is a disorder of the nervous system that leads to regression in development, especially in the areas of expressive language and hand use.
- Rett Syndrome occurs almost exclusively in girls and may be misdiagnosed as Autism or Cerebral palsy.
- An infant with Rett syndrome usually has normal development for the first 6-18 months.
- Chromosomal analysis may now be used to search for the gene mutations that cause Rett syndrome.
Definition
Rett syndrome is a disorder of the nervous system that leads to regression in development, especially in the areas of expressive language and hand use. In most cases, it is caused by a genetic mutation.
Causes, incidence, and risk factors
Rett Syndrome occurs almost exclusively in girls and may be misdiagnosed as Autism or Cerebral palsy.
The gene associated with Rett syndrome is on the X-chromosome. This gene contains instructions for creating methl-CpG-binding protein 2 (MeCP2), a protein that regulates the manufacture of various other proteins.
Mutations in the MeCP2 gene causes these other proteins to be produced incorrectly, which damages the maturing brain. Studies link mutations in this gene to 75% of Rett syndrome cases.
Females have two X chromosomes, so even when one has this significant mutation, the other X chromosome provides enough normal protein for the child to survive.
Males conceived with this mutation do not have a second X chromosome to compensate for the problem. Therefore, the mutation is usually lethal, leading to miscarriage, stillbirth, or very early death.
Most cases of the mutation arise spontaneously. However, there also seem to be some clusters within families and certain geographic regions, for example Norway, Sweden, and Northern Italy.
Symptoms
An infant with Rett syndrome usually has normal development for the first 6-18 months. Once symptoms do begin, they vary greatly from mild to severe. In fact, there are at least six variants that have been identified to date. In addition, there seem to be four distinct stages of the disease.
Symptoms may include:
- Hypotonia (floppy arms and legs) - frequently the first sign
- Slowing head growth beginning at approximately 5-6 months of age
- Developmental regression
- Severely impaired language development
- Loss of purposeful hand movements; for example, the pincer grasp used to pick up small objects is replaced by repetitive hand motions like hand wringing or constant placement of hands in mouth
- Apraxia - partial or complete inability to carry out purposeful movements
- Shaky, unsteady, or stiff gait; or toe walking
- Loss of social engagement
- Seizures (1/3 of patients)
- Intermittent hyperventilation with a disorganized breathing pattern, air swallowing, and breath holding
Written and revised by
Gerald Hurowitz, M.D.
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