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Rett Syndrome: A New Understanding of Neurological Disorders
by Jennifer Wider, MD

While the gene responsible for Rett Syndrome was discovered in 1999, only recently have researchers realized the potential for the finding to shed light on this and other neurological disorders. This pivotal research, along with lobbying efforts by actress Julia Roberts, has brought this once obscure disease to the political and scientific forefront. Since the discovery of the gene by Huda Zoghbi, M.D. and colleagues at Baylor College of Medicine, researchers have been working towards potential therapies and screening techniques.

Rett Syndrome occurs predominantly in females, affecting one in every 15,000 girls worldwide. Children with the disease will develop normally for the first 6 to 18 months, achieving anticipated developmental milestones, and then will begin to regress as their motor and cognitive skills cease to mature.

The mutation responsible for Rett Syndrome occurs on the tip of the X chromosome in a gene that researchers have named the MECP2. A child with the disease experiences marked neurological deterioration because components of the gene are responsible for normal brain development.

The disorder affects males and females differently because the mutation is located on the X chromosome, causing an uneven gender distribution as girls have two X chromosomes and boys have one X and one Y. The effects of the faulty gene can be offset in girls, to some extent, because the normal X will compensate. Thus, affected girls have the symptoms of the disease, but can survive the mutation. The Y chromosome in boys cannot compensate for the X chromosomal mutation and the defect is usually lethal. The disease is seen almost exclusively in girls because male pregnancies generally self-abort.

Those affected appear normal at birth and into the first year of life because, "The protein product of the gene is not needed by the nervous system until the neurons mature," explains Carolyn Schanen, MD, Ph.D., Head of Human Genetics Research Programs at the Alfred I. duPont Hospital for Children in Wilmington, DE. In other words, symptoms will only become apparent when the brain cells are mature.

Once neurons or brain cells begin to mature, sufferers will experience emotional withdrawal, loss of previously acquired speech and motor skills, delayed head growth, and, as the child ages, characteristic hand gestures, breathing abnormalities and walking problems. Ultimately, Rett Syndrome leaves affected girls dependent upon wheelchairs and only able to use eye gestures to communicate.

"It is important to note that the gene discovery has revealed that a subset of patients with several other disorders, such as mild mental retardation and psycho-affective disorders, have mutations in MECP2," said Dr. Zoghbi. The association with more common diseases like schizophrenia and bipolar disorder has led to a better understanding of the function and development of the human brain. Now, researchers can look for ways to normalize the defect at the cellular level.

Before the gene discovery, Rett Syndrome was often a clinical diagnosis made at the age of 7 or 8. Children would pass from one office to the next, misdiagnosed by doctors who failed to recognize the perplexing symptoms. Now, they can be treated earlier and taught to retain skills before they lose them.

Rett Syndrome occurs spontaneously in most girls and the risk of a family having a second child with the disease is very low. "Many families want a prenatal diagnosis," according to Dr. Schanen. In the past, "Some families even terminated pregnancies because of female gender. This is no longer an issue because genetic testing is a major assurance." A genetic counselor can be consulted for families who already have one daughter with Rett Syndrome, but routine screening is not recommended because there is currently no effective treatment.

Doctors are looking forward to a wide array of treatment alternatives for Rett Syndrome and the associated diseases. According to Dr. Zoghbi, "When effective therapeutic options become available, newborn screens can be put in place to identify affected individuals so that therapy can be started before most symptoms appear. Such early intervention holds the promise of better outcomes for at least some of the features of this class of disorders."

In working towards early intervention options, researchers have also begun to understand the significant role sex plays in varied congenital genetic disorders. Experts discussed Rett Syndrome and other disorders at the March 2002 scientific advisory meeting "Sex Begins in the Womb", hosted by the Society for Women's Health Research and Stanford University School of Medicine.

E-mail Sarahg@womens-health.org to receive more information about the Society for Women's Health Research scientific advisory meeting "Sex Begins in the Womb."

For more information, visit the International Rett Syndrome Association at http://www.rettsyndrome.org.

The Society for Women's Health Research is the nation's only not-for-profit organization whose sole mission is to improve the health of women through research. Founded in 1990, the Society brought to national attention the need for the appropriate inclusion of women in major medical research studies and the resulting need for more information about conditions affecting women. The Society advocates increased funding for research on women's health, encourages the study of sex differences that may affect the prevention, diagnosis and treatment of disease, and promotes the inclusion of women in medical research studies. Dr. Donnica Moore has been a member of the Society since 1990 and is a past member of its Board of Directors.

Created: 1/9/2003  -  Donnica Moore, M.D.

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