Blood Test For Rett Syndrome Now Available

A genetic test for Rett syndrome has been developed at Baylor College of Medicine.

Scientists at the Baylor DNA Diagnostic Laboratory developed the test after a team of Baylor researchers announced in September their discovery of the defective gene that causes Rett syndrome, a neurodevelopmental disorder that affects girls.

"Using a blood sample from someone suspected of having Rett syndrome, we can analyze the MECP2 gene on the X chromosome for the mutation that causes the disorder," says Dr. Benjamin Roa, acting director of the Baylor DNA Diagnostic Laboratory.

The presence of the mutation can confirm diagnosis of Rett syndrome. Blood samples from other family members can be screened for the mutation, but it is rare that the disorder is inherited because the mutation occurs at random.

The test requires an analysis of the entire MECP2 gene, a lengthy process that can take up to a month before results are available, Dr. Roa says. Physicians and genetic counselors can request the Rett test for patients by calling 800-226-3624. Insurance companies may vary on whether they will cover the cost, $950. If a mutation is identified in the affected individual, other family members may be studied at a lower cost of $250. As with all other tests for genetic diseases, genetic counseling is strongly recommended, Dr. Roa says.

Rett syndrome is one of the most common forms of mental retardation in females. Girls with the disorder appear to develop normally until 6 to 18 months of age. They then enter a period of regression, losing acquired speech and hand skills, and develop seizures, repetitive hand-wringing or hand-washing movements, irregular breathing and motor-control problems.

Current treatment for Rett syndrome is limited to physical, occupational and speech therapy to improve motor skills, medication to control seizures, and special diets to maintain adequate weight and meet nutritional needs.

Now that the genetic cause of Rett syndrome is known, researchers are looking for better treatments and possible ways to prevent the disorder, which affects approximately one in 10,000 females. Males with the Rett-related mutation on the X chromosome usually die before or shortly after birth because, unlike females, they have only one X chromosome.

Dr. Huda Y. Zoghbi and colleagues discovered the genetic cause of Rett syndrome. Dr. Zoghbi is a Baylor professor of pediatrics, molecular and human genetics, neurology and neuroscience, and a Howard Hughes Medical Institute investigator. She also is a pediatrician at Texas Children's Hospital and Ben Taub General Hospital.

The Rett test is one of more than 30 genetic tests available from the Baylor DNA Diagnostic Laboratory.

- B. J. ALMOND

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©2006 Texas Medical Center

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