Rett syndrome, often abbreviated RS or RTT, is a serious developmental disorder that appears almost exclusively in girls and persists throughout life. Children with RS progressively lose communication skills and purposeful hand movements; develop involuntary repetitive hand movements such as hand wringing, hand clapping, or finger rubbing; and have cognitive (intellectual) disabilities. Other symptoms of RS include apraxia (the inability to perform certain voluntary movements), seizures, breathing difficulties, slowed growth, difficulty crawling or walking, teeth grinding, and sleep disorders.
RS strikes all ethnic groups. Scientists estimate that RS occurs worldwide in 1 of every 10,000 to 23,000 girls born.
Andreas Rett, an Austrian physician, first described RS in 1966. However, medical professionals did not widely recognize the syndrome until Bengt Hagberg, a Swedish physician, published a description in 1983.
Symptoms.
The age at which RS first appears varies for different children, as do the course of its development and the severity of its symptoms. For most children with RS, early growth and development appear normal after birth. By 6 to 18 months of age, however, language and communication skills begin to decline. During this time, the head grows more slowly than normal, and the child eventually loses voluntary, purposeful use of the hands. Repetitive patterns of hand movements develop and may become nearly constant. Children with RS may have intellectual disabilities. However, many RS children are unable to speak and move well, making it difficult for physicians to assess their intellectual abilities. Some girls with RS exhibit behaviors similar to autism, a developmental disorder characterized by a limited ability to communicate and interact with other people. See Autism .
Physicians diagnose RS after observing many of the symptoms that characterize the disorder. However, they often misdiagnose RS as autism, cerebral palsy, or some other developmental disorder.
Cause.
Medical researchers have discovered that RS is caused by a mutation (change) in a gene called MECP2. Each of a person’s genes appears on one of 23 pairs of chromosomes. The MECP2 gene appears on the X chromosome, one of the two chromosomes that determine a person’s sex. The other is the Y chromosome. Males have one X chromosome and one Y chromosome, and females have two X chromosomes. Physicians use tests to identify mutations of the MECP2 gene. However, the presence of the MECP2 mutation alone does not constitute a diagnosis of RS—physicians must also observe the syndrome’s symptoms.
Scientists know the MECP2 gene regulates the activity of other genes. A mutation in this gene causes this regulatory function to fail, enabling the other genes to function abnormally. Scientists think that the mutation damages the MECP2 gene’s ability to regulate genes involved in brain development, causing the symptoms of RS. Similar MECP2 mutations appear in children with autism and various types of intellectual disabilities.
RS occurs only rarely in males. Because males have only one X chromosome, the MECP2 mutation harms them even more severely than it does females. Females have a normal copy of the gene on one X chromosome to help counteract the effects of the abnormal copy. Boys born with the mutated gene have no such protection and usually die shortly after birth. Medical experts have observed RS in boys who inherit an abnormal extra X chromosome or who develop a MECP2 mutation early in fetal development.
Treatment.
Physicians have yet to develop a specific treatment or cure for RS, but they may prescribe drugs to help control many of its symptoms. Physical therapy aimed at increasing mobility and reducing apraxia can also help people with RS. Most girls with RS require assistance for most activities of daily living, but they can often learn to do some things for themselves. Some RS children can use electronic devices to communicate, while others learn to communicate using their eyes. With assistance, some children with RS can take part in social, educational, and recreational activities. Scientists are studying the biology of RS in the hope of developing specific treatments for the disorder.
